lxfb/gxfb: when blanking with FB_BLANK_POWERDOWN, also turn off the CRT

The Display Control's CRT_EN can be shut off when we enter FB_BLANK_POWERDOWN
in an attempt to save additional power.

Signed-off-by: Andres Salomon <dilinger@debian.org>
Cc: 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>