neofb: kill some redundant code

Move common code outside if/else or switch/case clauses.

Drop checks done twice inside the neofb_check_var().

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