[RenderScript] Use OVERRIDE_RS_DRIVER string in the default
implementation.

Bug: 37035983
Test: mm
Test: manually push to sailfish & angler, verify GPU driver successfully
load, and tests are passing.

Change-Id: Ic55c74228e7eae599702365c513009aa3454656b
Merged-In: Ic55c74228e7eae599702365c513009aa3454656b
3 files changed