USB: clean up some host controller sparse warnings

Fix usb sparse warnings:

drivers/usb/host/isp1362-hcd.c:2220:50: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-mem.c:43:24: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-mem.c:49:24: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-mem.c:161:24: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-mem.c:198:16: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-mem.c:319:31: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-mem.c:1231:33: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-pci.c:177:23: warning: non-ANSI function declaration of function 'xhci_register_pci'
drivers/usb/host/xhci-pci.c:182:26: warning: non-ANSI function declaration of function 'xhci_unregister_pci'
drivers/usb/host/xhci-ring.c:342:32: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-ring.c:525:34: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-ring.c:1009:32: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-ring.c:1031:32: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-ring.c:1041:16: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-ring.c:1096:30: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-ring.c:1100:27: warning: Using plain integer as NULL pointer
drivers/usb/host/xhci-mem.c:224:27: warning: symbol 'xhci_alloc_container_ctx' was not declared. Should it be static?
drivers/usb/host/xhci-mem.c:242:6: warning: symbol 'xhci_free_container_ctx' was not declared. Should it be static?

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Lothar Wassmann <LW@KARO-electronics.de>
Signed-off By: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 16ef5fd..9e27eb0 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -388,7 +388,7 @@
 		cur_seg = cur_seg->next;
 		if (cur_seg == start_seg)
 			/* Looped over the entire list.  Oops! */
-			return 0;
+			return NULL;
 	}
 	return cur_seg;
 }
@@ -582,7 +582,7 @@
 	struct xhci_ring *ep_ring;
 	struct xhci_virt_ep *ep;
 	struct list_head *entry;
-	struct xhci_td *cur_td = 0;
+	struct xhci_td *cur_td = NULL;
 	struct xhci_td *last_unlinked_td;
 
 	struct xhci_dequeue_state deq_state;
@@ -1115,7 +1115,7 @@
 
 	do {
 		if (start_dma == 0)
-			return 0;
+			return NULL;
 		/* We may get an event for a Link TRB in the middle of a TD */
 		end_seg_dma = xhci_trb_virt_to_dma(cur_seg,
 				&cur_seg->trbs[TRBS_PER_SEGMENT - 1]);
@@ -1137,7 +1137,7 @@
 						 suspect_dma <= end_trb_dma))
 					return cur_seg;
 			}
-			return 0;
+			return NULL;
 		} else {
 			/* Might still be somewhere in this segment */
 			if (suspect_dma >= start_dma && suspect_dma <= end_seg_dma)
@@ -1147,7 +1147,7 @@
 		start_dma = xhci_trb_virt_to_dma(cur_seg, &cur_seg->trbs[0]);
 	} while (cur_seg != start_seg);
 
-	return 0;
+	return NULL;
 }
 
 static void xhci_cleanup_halted_endpoint(struct xhci_hcd *xhci,
@@ -1223,11 +1223,11 @@
 	struct xhci_ring *ep_ring;
 	unsigned int slot_id;
 	int ep_index;
-	struct xhci_td *td = 0;
+	struct xhci_td *td = NULL;
 	dma_addr_t event_dma;
 	struct xhci_segment *event_seg;
 	union xhci_trb *event_trb;
-	struct urb *urb = 0;
+	struct urb *urb = NULL;
 	int status = -EINPROGRESS;
 	struct xhci_ep_ctx *ep_ctx;
 	u32 trb_comp_code;