mailbox: arm_mhu: add driver for ARM MHU controller

Add driver for the ARM Primecell Message-Handling-Unit(MHU) controller.

Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
Signed-off-by: Andy Green <andy.green@linaro.org>
Signed-off-by: Vincent Yang <vincent.yang@socionext.com>
Signed-off-by: Tetsuya Nuriya <nuriya.tetsuya@socionext.com>
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index 2e79231..b18201e 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -2,6 +2,8 @@
 
 obj-$(CONFIG_MAILBOX)		+= mailbox.o
 
+obj-$(CONFIG_ARM_MHU)	+= arm_mhu.o
+
 obj-$(CONFIG_PL320_MBOX)	+= pl320-ipc.o
 
 obj-$(CONFIG_OMAP2PLUS_MBOX)	+= omap-mailbox.o