[ARM] 5118/1: pxafb: add exit and remove handlers

This patch adds exit and remove handlers to pxafb so that it can be loaded
and unloaded as a module.

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