defconfig: msm: Enable KPTI on sa8155, sm8150

Enable KPTI mitigation on sa8155, sm8150 since it
is needed as part of android CTS. The mitigation
is to unmap kernel when running in userspace.

Change-Id: I3ef97a7646ff07c1a7086c0aaaf069fc2bdef253
Signed-off-by: Kaushal Kumar <kaushalk@codeaurora.org>