common: make cpaccess module code writeable

cpaccess has self-modifying code. This does not work when
CONFIG_DEBUG_SET_MODULE_RONX is set and cpaccess is built
as a module, because the text section is marked not writeable.
Call mm function to make the modified instruction writeable.

Change-Id: I317ab55cd6bdceae429ad89629818ab5f7f99599
Signed-off-by: Neil Leeder <nleeder@codeaurora.org>