backlight: Add Epson L4F00242T03 LCD driver

The Epson LCD L4F00242T03 is mounted on the Freescale i.MX31 PDK board. 
Based upon Marek Vasut work in l4f00242t03.c, this driver provides
basic init and power on/off functionality for this device through the
sysfs lcd interface.

Unfortunately Datasheet for this device are not available and
all the control sequences sent to the display were copied from the
freescale driver that in the i.MX31 Linux BSP.

As in the i.MX31PDK board the core and io suppliers are voltage
regulators, that functionality is embedded here, but not strict.

Signed-off-by: Alberto Panizzo <maramaopercheseimorto@gmail.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>