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 <[email protected]>
[[email protected]: ack for staging part]
Acked-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Omar Ramirez Luna <[email protected]>
Signed-off-by: Suman Anna <[email protected]>

drivers/remoteproc/Kconfig

@@ -14,8 +14,9 @@ config OMAP_REMOTEPROC
 	depends on HAS_DMA
 	depends on ARCH_OMAP4 || SOC_OMAP5
 	depends on OMAP_IOMMU
-	depends on OMAP_MBOX_FWK
 	select REMOTEPROC
+	select MAILBOX
+	select OMAP2PLUS_MBOX
 	select RPMSG
 	help
 	  Say y here to support OMAP's remote processors (dual M3

drivers/remoteproc/omap_remoteproc.c

@@ -27,8 +27,8 @@
 #include <linux/platform_device.h>
 #include <linux/dma-mapping.h>
 #include <linux/remoteproc.h>
+#include <linux/omap-mailbox.h>
 
-#include <plat/mailbox.h>
 #include <linux/platform_data/remoteproc-omap.h>
 
 #include "omap_remoteproc.h"