cirrusfb: remove unused variables

After commit a1d35a7a

 (cirrusfb: use modedb and add mode_option
parameter), these variables are no longer used, so remove them to fix
compilation warning.

Signed-off-by: Vlada Periæ <vlada.peric@gmail.com>
Acked-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>