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/drivers/remoteproc/Kconfig b/drivers/remoteproc/Kconfig
index d4d377c..ce1743d 100644
--- a/drivers/remoteproc/Kconfig
+++ b/drivers/remoteproc/Kconfig
@@ -14,8 +14,9 @@
 	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