video: lm3530_bl: Introduce new tunables to control LED driver

- min_br: sets the mininum brightness level (2-114)
- max_br: sets the maximum brightness level (2-114)
- br_mode: sets the linear (default 1) or exponential (0) brightness
mapping mode.

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>

Conflicts:
	drivers/video/backlight/lm3530_bl.c

	modificado: arch/arm/mach-msm/lge/mako/board-mako-display.c
	modificado: drivers/mmc/core/core.c
	modificado: drivers/video/backlight/lm3530_bl.c