This patch fixes a bug where we obtain a smaller resolution than requested.
(eg: in 640x480, only 639x479 usable pixels).

This was due to 1 being substracted from the xres and yres vars two times:
first in mbxfb.c and then in the macros from reg_bits.h.

This patch removes the minus ones from the mbxfb.c file. Tested and works.
Signed-off-by: Raphael Assenat <raph@8d.com>
Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>