defconfig: Enable MSM_AVS_HW on 8960 targets

AVS fine tunes the processor core voltage based on the current
system conditions and process technology.

Change-Id: Ia44acfa82bf921632d66576f9028bb4abfe976b5
Signed-off-by: Praveen Chidambaram <pchidamb@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>