atmel_lcdfb: wiring BGR to RGB color mode

Adds different wiring mode for the LCD screen.

The legacy atmel LCDC IP uses a non standard color mode, "BGR-555.1" instead
"RGB-565".  The major part of graphic stacks for embedded systems uses only
"RGB-565".  It is possible to swap LCD IOs instead of doing this bit swapping
by software (See application note AT91SAM9 LCD Controller
http://www.atmel.com/dyn/resources/prod_documents/doc6300.pdf)

This wire swapping is done on the at91sam9rl-ek board (board code
using this patch will come later).

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Hans-Christian Egtvedt <hcegtvedt@atmel.com>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Andrew Victor <avictor.za@gmail.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>