Revert "mm: protect against PTE changes done by dup_mmap()"

This reverts commit a9e3a1ab.

Reason for revert: remove SPF non upstream code
Bug: 140544941
Test: boot
Change-Id: I912a8891ac6cf3e72c7b7aa27df2922554b31491
Signed-off-by: Martin Liu <liumartin@google.com>
[dereference23: Forward port to msm-5.4]
Signed-off-by: Alexander Winkowski <dereference23@outlook.com>