Gamma Corrected Brightness: Recalculate backlight intensity based on gamma presets

Thanks to Yorici for gamma info + making me do this :)

sysfs:
/sys/module/lm3630_bl/parameters/gamma_correction
/sys/module/lm3630_bl/parameters/cur_level

gamma_correction:
	0 - Stock
	1 - Gamma 2.0
	2 - Gamma 2.2 (recommended)
	3 - Gamma 3.0
cur_level = current backlight value

Change-Id: I414876b7f68b56f87977e1910ed3774003fb6745