fbdev: blackfin has __raw I/O accessors, so use them in fb.h

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>