BACKPORT: FROMLIST: mm: ASLR: use get_random_long()

(cherry picked from commit https://lkml.org/lkml/2016/2/4/833

)

Replace calls to get_random_int() followed by a cast to (unsigned long)
with calls to get_random_long().  Also address shifting bug which, in case
of x86 removed entropy mask for mmap_rnd_bits values > 31 bits.

Bug: 26963541
Signed-off-by: Daniel Cashman <dcashman@android.com>
Signed-off-by: Daniel Cashman <dcashman@google.com>
Change-Id: Iac34b63294ec120edcbf8760186667a84a5cf556