This patch fixes a possible barriers problem in RDAC_WR functions, then
remove redudant ones.

It also removes one unneeded register load from blitter function().
Signed-off-by: NKrzysztof.Helt <krzysztof.h1@wp.pl>
Signed-off-by: NAntonino Daplas <adaplas@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>