mailbox/omap: move the OMAP mailbox framework to drivers

The mailbox hardware (in OMAP) uses a queued mailbox interrupt
mechanism that provides a communication channel between processors
through a set of registers and their associated interrupt signals
by sending and receiving messages.

The OMAP mailbox framework/driver code is moved to be under
drivers/mailbox, in preparation for adapting to a common mailbox
driver framework. This allows the build for OMAP mailbox to be
enabled (it was disabled during the multi-platform support).

As part of the migration from plat and mach code:
- Kconfig symbols have been renamed to build OMAP1 or OMAP2+ drivers.
- mailbox.h under plat-omap/plat/include has been split into a public
  and private header files. The public header has only the API related
  functions and types.
- The module name mailbox.ko from plat-omap is changed to
  omap-mailbox.ko
- The module name mailbox_mach.ko from mach-omapX is changed as
    mailbox_omap1.ko for OMAP1
    mailbox_omap2.ko for OMAP2+

Cc: Tony Lindgren <tony@atomide.com>
[gregkh@linuxfoundation.org: ack for staging part]
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Omar Ramirez Luna <omar.ramirez@copitl.com>
Signed-off-by: Suman Anna <s-anna@ti.com>
diff --git a/arch/arm/mach-omap2/devices.c b/arch/arm/mach-omap2/devices.c
index 4c97a86..73762ac 100644
--- a/arch/arm/mach-omap2/devices.c
+++ b/arch/arm/mach-omap2/devices.c
@@ -328,7 +328,7 @@
 	return 0;
 }
 
-#if defined(CONFIG_OMAP_MBOX_FWK) || defined(CONFIG_OMAP_MBOX_FWK_MODULE)
+#if defined(CONFIG_OMAP2PLUS_MBOX) || defined(CONFIG_OMAP2PLUS_MBOX_MODULE)
 static inline void __init omap_init_mbox(void)
 {
 	struct omap_hwmod *oh;
@@ -352,7 +352,7 @@
 }
 #else
 static inline void omap_init_mbox(void) { }
-#endif /* CONFIG_OMAP_MBOX_FWK */
+#endif /* CONFIG_OMAP2PLUS_MBOX */
 
 static inline void omap_init_sti(void) {}