[PARISC] stifb: Fix framebuffer console at 32bpp

Fix stifb framebuffer console at 32bpp on a HCRX-24 card
by properly setting DIRECTCOLOR. Also a few nice cleanups
to the code.

Signed-off-by: Helge Deller <deller@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>