fbdev: Fix logo if logo depth is less than framebuffer depth

The VGA16 logo (bpp = 4) and monochrome logo (bpp = 1) do not contain any
color information (no CLUT).  If the fb depth is > logo depth, these logo's
will not properly display. Fix by using the console palette instead of
creating a new one.

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>