defconfig: 8916: Disable kmemleak task stack and module scan

Enable kmemleak at bootup and disable task stack and module
scan by default. Task stack and module scan can result
in code running with irq/preemption disabled for considerable
amount of time.

Change-Id: If49b1a6da1e10df3632dc9e0db2ec0bdbce8f474
Signed-off-by: Vignesh Radhakrishnan <vigneshr@codeaurora.org>