fbdev: fix typo in drivers/video/modedb.c

When I viewed drivers/video/modedb.c, I noticed a very old typo already
contained in 2.6.0.

This typo remained unheeded at least 5 years.  Clear evidence of its
importance.  ;)

Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>