pxafb: convert fb driver to use ioremap() and __raw_{readl, writel}

This is part of the effort moving peripheral registers outside of pxa-regs.h,
and using ioremap() make it possible the same IP can be re-used on different
processors with different registers space

As a result, the fixed mapping in pxa_map_io() is removed.

The regs-lcd.h can actually moved to where closer to pxafb.c but some of its
bit definitions are directly used by various platform code, though this is not
a good style.

Signed-off-by: eric miao <eric.miao@marvell.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>