ARM: dts: msm: Select alternative secure context bank for SDM670

Select alternative context bank for secure playback on SDM670 1.0.
This is needed to allow the GPU in secure mode with the
mentioned SID in alternative context bank.

Change-Id: I9b233b027c9ea6bc967bf6b85c62662418f966fa
Signed-off-by: Rajesh Kemisetti <rajeshk@codeaurora.org>