defconfig: msm: Enable SSBD config for Atoll

Enable Speculative Store Bypass Disable config for Atoll,
so that the mitigation can be used for its impacted cores.
Enabling this config is required, to ensure that PSTATE.SSBS
is set for EL0, so that speculation is enabled for it.

Change-Id: I886d2b383bc6247e854ce8cfa3f8948881544e82
Signed-off-by: Mayank Grover <groverm@codeaurora.org>