fbdev: s3fb: Revert mclk stop in suspend

There are systems which want to wait for as long as it takes for the
stopped video memory to answer. Mapping it out helps to avoid that
while the system is running but standby still hangs somehow. So just
leave the memory on in standby same as it was before my change.

Signed-off-by: Zsolt Kajtar <soci@c64.rulez.org>
Signed-off-by: Helge Deller <deller@gmx.de>