PowerManagerService: fix getAutoBrightnessValue for btn/kbd

getAutoBrightnessValue calculations are correct only for LCD
backlight brightness values increasing with higher light values.
Skip the calculation for the reversed button/keyboard backlight
arrays, where the backlight brightness decreases with increasing
light values.

Change-Id: Ib72b8325fe2b0f83780e91dc94eea2e38061224b
fix an overflow in the orientation sensor calculations

this would cause the TYPE_ORIENTATION sensor to report NaN after
40 to 800 hours of up-time. this problem only affects the older
and deprecated SensorListener API.

Bug: 7434842
Change-Id: Ie8593cca9c98e4907e417db4106c06151e3ee9a1