carminefb: fix possible access beyond end of carmine_modedb[]

This check is off-by-one.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
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>