neofb: drop the xtimings structure

Remove the xtimings structure which only stored some values to be used
later (mostly once).  Calculate and use these values in places they are
needed.

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>