svgalib: mode selection updates

This patch changes mode selection matching algorithm.  It allows to choose
mode with matching depth even when requested color lengths are greater than
color lengths of every mode with requested color depth.

It also fixes bug in s3fb - wrong error value returned when format is not
supported by chip.

Signed-off-by: Ondrej Zajicek <santiago@crfreenet.org>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>