viafb: fix hardware acceleration for suspend & resume

This patch splits the acceleration initialization in two parts:
The first is only called during probe and is used to allocate
resources. The second part is also called on resume to reinitalize
the 2D engine. This should fix all acceleration issues after resume
most notable an "invisible" cursor and as we do nothing special it is
reasonable to assume that it works on all supported IGPs.

Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Acked-by: Jonathan Corbet <corbet@lwn.net>
Cc: Joseph Chan <JosephChan@via.com.tw>