Within the device-configuration file, a device can specify a
point along the brightness mapping as the beginning of high-brightness
mode. All points in the mapping beyond that range will be treated
as high-brightness-mode points. Normal brightness range will end
at the specified point.
Bug: 131813802
Test: Verify brightness works through the entire pre-HBM range, with and
without new specifier.
Change-Id: I4d9c6fab1c1f11e550ee33643673b004ee54dbfe
6e8de44e86