mm: Fix incorrect cache attribute restoration.

armv7 uses cache policy as WRITEALLOC. CPA is
restoring the cache attributes to WRITEBACK during
set_pages_array_wb().
Fixed issues in pmd to pte prot translation and vice versa.

Change-Id: I8406b784f62d559f657ef7bc08e77c83ac6e5690
Signed-off-by: Krishna Reddy <vdumpa@nvidia.com>
Reviewed-on: http://git-master/r/122472
Reviewed-by: Simone Willett <swillett@nvidia.com>
Tested-by: Simone Willett <swillett@nvidia.com>