defconfig: apq8084: disable debug options

Certain debug options and features are unnecessary for the
perf_defconfig and degrade the performance. Disable these to
increase the performance.

Disable KSM for defconfig because the feature is not
required on 8084.

Change-Id: I76cb1b12e88dbd2c22589aa78762a2497909f594
Signed-off-by: Vince Leung <vincentl@codeaurora.org>