viafb: merge viafb_update_viafb_par in viafb_update_fix

Shrink and merge viafb_update_viafb_par.  This removes a lot of duplicated
data in viafb_par.  Use the relevant data of fb_info instead.  On the way
it removes an inconsistency in handling a second framebuffer which only
worked because viafbinfo1->par is modified to point to the same viafb_par
as viafbinfo->par.

Code cleanup only, no runtime change expected.

Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Cc: Scott Fang <ScottFang@viatech.com.cn>
Cc: Joseph Chan <JosephChan@via.com.tw>
Cc: Harald Welte <laforge@gnumonks.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>