gxfb: don't enable the CRT DACs when we are in flatpanel mode

When the FP strap is enabled, don't turn on the CRT DACs - that will save
about 35 mA of power.

Updated/cleaned up by Andres Salomon.

Signed-off-by: Andres Salomon <dilinger@debian.org>
Signed-off-by: Jordan Crouse <jordan.crouse@amd.com>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>