lcd: allow lcd device to handle mode change events

Some LCD panels are capable of different resolutions, and is allowed
to change at run-time, so to make "struct lcd_device" to be able to
handle mode change events here.

Signed-off-by: Eric Miao <eric.miao@marvell.com>
Acked-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>