nvidiafb: adjust flags to take advantage of new scroll method

The SCROLL_MOVE method has been optimized such that it is significantly faster
than SCROLL_REDRAW.  Adjust flags to indicate that blitting is preferred over
rendering.

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>