[PATCH] tgafb: support the DirectColor visual

 The 32-plane variations of the TGA use the Bt463 RAMDAC and are therefore
DirectColor rather than TrueColor adapters.  This is a set of changes to
implement the necessary bits to support this model.  A couple of fixes to fix
accesses to the RAMDAC are included as a side-effect.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: James Simmons <jsimmons@infradead.org>
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>