s5: enable s5 mbox driver [3/3]

PD#SWPL-81348

Problem:
s5 mbox driver not enabled

Solution:
enable mbox driver

Verify:
pxp

Change-Id: I83a2586d7f743a08243ba86a8583be1b023a7591
Signed-off-by: Shunzhou Jiang <shunzhou.jiang@amlogic.com>
2 files changed