ARM: 8823/1: Implement pgprot_device()

This is used when mmapping the PCI resource* files in sys.  Because ARM
currently lacks an implementation of pgprot_device(), it falls back to
pgprot_uncached() (Strongly Ordered), but we should be able to use
Device memory instead.

Doing this speeds up large writes to the resource files by about 40% on
one of my systems.  It also ensures that mmaps on these resources use
the same memory type as ioremap().

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>