Directly register for prox as the secondary sensor

Instead of binned brightness.
The new binned brightness sensor doesn't report prox, so
we won't see the white dot when we're in AOD2 (ie: docked, pulsing
notification).

Test: manual
Bug: 194151347
Change-Id: I2c7547334889dbda462a075d62504c9e745b118a
1 file changed