atmel_lcdfb: suspend/resume support

Teach atmel_lcdfb driver how to suspend/resume.

Note that the backlight control should probably do more of the same stuff:
turning off display power (more than just the backlight) and stopping the
clocks (and dma to drive the no-longer-seen display).  No point in wasting
power to generate images that can't be observed, after all...

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
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>