defconfig: msm: update mmap randomness for sdm660

CTS malloc tests on Android 'N' expects higher entropy in
mmap returned address. Present value of mmap random bits
is not providing enough variations for 32 bit tasks.

Increase mmap_rnd_bits for 32bit and mmap_rnd_compat_bits
for 64bit targets to value of 16.

Change-Id: I1cb88cb1f1fc2a8dc7e27eb54b8c0b2a3eb37843
Signed-off-by: Shiraz Hashim <shashim@codeaurora.org>