sil24 0.20 didn't use to perform (what seems to be) port multiplier
initialization and controller reset 0.10 driver does.  This makes some
sil24 controllers malfunction.  This patch adds PM initialization and
controller resetting to initilization and bumps version to 0.21.
Please refer to the following thread for more information.

http://marc.theaimsgroup.com/?l=linux-ide&m=112582819830324&w=2
http://marc.theaimsgroup.com/?l=linux-ide&m=112636045531060&w=2Signed-off-by: NTejun Heo <htejun@gmail.com>
Signed-off-by: NJeff Garzik <jgarzik@pobox.com>