lcd: add platform_lcd driver

Add a platform_lcd driver to allow boards with simple lcd power controls
to register themselves easily.

[akpm@linux-foundation.org: build fix]
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>