viafb: remove temporary start address setting

Currently the start address is set to an initial value every time
viafb_setmode is called.

This is not done consistently along graphic cores and not even the whole
address but often only parts of it.  On top of that it seems useless as
the real/final address will be set by viafb_set_start_addr a few lines
later.

Remove this superfluous initalization to shrink register initalization and
as a start to decouple primary and secondary display.  Code cleanup, no
notable 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>