soc: qcom: protect kernel text from other bus masters

Add provision to enable mpu based kernel text region
protection from other bus masters so that they cannot
over-write kernel code.

Since this is mpu based, any write access to kernel text
region by other masters (than cpu) would result into a bus
error.

Change-Id: I026590cb68d03dd74662efeb61c77f76e0d8060f
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>