Fix the PCIGART increment and add a cpu_to_le32 for ppc (untested)

Paulus was unsure if we need to cpu_to_le32 but the old code was definitely
wrong, so make it consistent and let the PPC guys figure it out later.
Signed-off-by: NDave Airlie <airlied@linux.ie>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>