viafb: rename output devices

Now it looks like we finally know enough about the output devices to give
them proper names. As VIA_96 is often referred to as DVP0 rename it to
VIA_DVP0. As VIA_6C and VIA_93 seem to exist only on CLE266 and "replace"
DVP0 and DVP1 there rename them to VIA_LDVP0 and VIA_LDVP1 (L as legacy).
The proc names were changed accordingly which should be harmless as they
were just introduced and not beyond RFC state.
This patch should make things a bit more comfortable and less scary.

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