defconfig: msm8916-64bit: Enable Kmemleak by default

Enable kmemleak at bootup and allocate an early
log size of 4000.

Additionally, disable kmemleak task stack scan and
module scan by default. Else this can result in the
code running for considerable amount of time with
irq/preemption disabled.

Change-Id: I9acf1c9340b4f2fe09b1f7eeb4583665f3208d71
Signed-off-by: Vignesh Radhakrishnan <vigneshr@codeaurora.org>