defconfig: msm: Enable PBS driver support for sdm660

PBS driver triggers the PBS event specified by the client
driver to execute the PBS RAM configuration. Enable it for
sdm660 targets.

Change-Id: I95c70295805d31506c864546b763bef8a5e7b4bf
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>