Improve atyfb_atari_probe():
* Call correct_chipset() so that more par members, par->features in
  particular, get initialized.
* If probe fails iounmap() the mapped regions and continue probing for more
  adapters.

Only verified to cross-compile due to lack of hardware.
Signed-off-by: Ville Syrjala <syrjala@sci.fi>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>