fbdev: atafb - Fix 16 bpp console

  - 16 bpp must use the cfb_*() ops
  - 16 bpp needs to set up info->pseudo_palette[] (was fbcon_cfb16_cmap[] in
    2.4.x)
  - Kill commented out 2.4.x fbcon remnants

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>