omap: mailbox: convert block api to kfifo

The underlying buffering implementation of mailbox
is converted from block API to kfifo due to the simplicity
and speed of kfifo.

The default size of the kfifo buffer is set to 256 bytes.
This value is configurable at compile time (via
CONFIG_OMAP_MBOX_KFIFO_SIZE), and can be changed at
runtime (via the mbox_kfifo_size module parameter).

Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: Hari Kanigeri <h-kanigeri2@ti.com>
Signed-off-by: Hiroshi DOYU <Hiroshi.DOYU@nokia.com>
diff --git a/arch/arm/plat-omap/Kconfig b/arch/arm/plat-omap/Kconfig
index 78b49a6..111d39a 100644
--- a/arch/arm/plat-omap/Kconfig
+++ b/arch/arm/plat-omap/Kconfig
@@ -106,6 +106,15 @@
 	  Say Y here if you want to use OMAP Mailbox framework support for
 	  DSP, IVA1.0 and IVA2 in OMAP1/2/3.
 
+config OMAP_MBOX_KFIFO_SIZE
+	int "Mailbox kfifo default buffer size (bytes)"
+	depends on OMAP_MBOX_FWK
+	default 256
+	help
+	  Specify the default size of mailbox's kfifo buffers (bytes).
+	  This can also be changed at runtime (via the mbox_kfifo_size
+	  module parameter).
+
 config OMAP_IOMMU
 	tristate