arm: mmap: remove the redundant check of personality

Fixes the merge "Merge tag 'lsk-v3.18-15.12-android' into 'msm-3.18'".
The above mentioned merge wrongly removed part of a fix that was picked
from upstream (arm: factor out mmap ASLR into mmap_rnd). Ressurect the
fix.

Change-Id: I9cc0057652048dafbe45f7af63a4b5117076ec76
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>