pm2fb: panning and hardware cursor fixes

This patch:
- disallows setting of virtual height above 2048 as it does
  not work for accelerated copyarea and imageblit
- fixes blinking of pm2v cursor by pushing cursor outside
  the display (x=2047)
- fixes hardware cursor position on Permedia 2 chips with
  panning enabled
- enables hardware cursor by default

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>