pm3fb: 3 small fixes

This patch contains 3 small improvements:
- it corrects scan line width calculation in pm3fb_imageblit()
- it corrects mmio mapping for big endian machines
- it enables panning acceleration constants

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>