i810fb: fix stack exploding

Alan Cox has found that the i810fb function "uses a whopping 2.5K of stack".

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Reported-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>