arm: mm: program ptes for access restriction

CONFIG_RODATA allows strict kernel mapping permissions to
be followed and accordingly maps regions as read-only,
not-executable etc. correspondingly. CONFIG_RODATA however
assumes all memory regions to be SECTION_SIZE aligned and
section mapped for performance reasons.

With CONFIG_FORCE_PAGES, we force all kernel mappings as
page mapped thus breaking CONFIG_RODATA.

Provide provision to apply permissions at page (pte)
level, if CONFIG_RODATA does not find section mapping.

Change-Id: I8dbf5c3741836bc63a231d8a471cf0306662993b
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>