fbdev: sh_mobile_lcdcfb: Enable 32 bpp and 24 bpp support

This patch extends the LCDC driver with 24 bpp
and 32 bpp support.

These modes have been kept disabled earlier due
to dependencies between the potential two LCDC
channels that are exported as two separate
framebuffer devices. The dependency boils down
to a byte swap register that is shared between
multiple channels.

With this patch applied all single channel LCDC
hardware can chose freely from 16, 24 and 32 bpp.
Dual channel LCDC must stick to the same setup
for both channels.

Without this patch only 16 bpp is fully supported.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>