fbcon: smart blitter usage for scrolling

This patch replaces the current SCROLL_MOVE method with smarter method using
the same logic as the SCROLL_REDRAW method.  This brings these two methods
much closer in performance and benefits all framebuffers which uses the
SCROLL_MOVE method.

[adaplas]
- remove unnecessary char attribute checking
- whitespace cleanups and 80-column line fixes

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>