viafb: some dvi cleanup

Remove some unused variables, move some dvi code around and store the
detected maximum resolution for later use.  The vertical resolution is
handled as the old code did it but I hope it can be read from the hardware
some day.

No runtime change expected.

Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Cc: Joseph Chan <JosephChan@via.com.tw>
Cc: Scott Fang <ScottFang@viatech.com.cn>
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>