defconfig: arm64: enable CONFIG_MSM_AVTIMER

It enables to read avtimer values using the avtimer driver so
ISP can switch to avtimer timestamps for the buffers when
VideoTelephony(VT) is used.

Change-Id: Ia717200f9b5cf865012ee2a58d1808ad1cb19d2d
Signed-off-by: Laxminath Kasam <lkasam@codeaurora.org>
Signed-off-by: Kuirong Wang <kuirongw@codeaurora.org>