uvesafb incorrectly sets the length of the color fields to 6 bits for
PSEUDOCOLOR modes, even though 8 bits are always used per pixel.  Fix this
by setting the length to 8.

The switch of the DAC width from the default 6 bits to 8 bits is retained
and tracked internally in the driver, but never exposed to userspace.
Signed-off-by: NMichal Januszewski <spock@gentoo.org>
Acked-by: NKrzysztof Helt <krzysztof.h1@poczta.fm>
Cc: <syrjala@sci.fi>
Cc: Geert Uytterhoeven <geert.uytterhoeven@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>