lcd: add SPI-based LCD and backlight driver for SHARP corgi/spitz

The driver is based on different source files including corgi_ssp.c,
corgi_lcd.c and corgi_bl.c, previously authored by Richard Purdie
and many others.

The LCD and Backlight device actually share the same SPI device, so
they are made into this single driver.

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>