atmel_lcdfb: set ypanstep to 1 and enable y-panning on AT91

Panning in the y-direction can be done by simply changing the DMA base
address.  This code is already in place, but FBIOPAN_DISPLAY will
currently fail because ypanstep is 0.

Set ypanstep to 1 to indicate that we do support y-panning and also set
the necessary acceleration flags on AT91 (AVR32 already have them.)

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>