powerpc: Fix a number of sparse warnings

Address some of the trivial sparse warnings in arch/powerpc.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index f03770e..79ba9b7 100644
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -325,7 +325,7 @@
 							 NULL);
 			if (lsizep != NULL)
 				lsize = *lsizep;
-			if (sizep == 0 || lsizep == 0)
+			if (sizep == NULL || lsizep == NULL)
 				DBG("Argh, can't find dcache properties ! "
 				    "sizep: %p, lsizep: %p\n", sizep, lsizep);
 
@@ -347,7 +347,7 @@
 							 NULL);
 			if (lsizep != NULL)
 				lsize = *lsizep;
-			if (sizep == 0 || lsizep == 0)
+			if (sizep == NULL || lsizep == NULL)
 				DBG("Argh, can't find icache properties ! "
 				    "sizep: %p, lsizep: %p\n", sizep, lsizep);