There seems to be no way to obtain device signature from sil24 after
SATA phy reset and SRST is needed anyway for later port multiplier
suppport.  This patch converts sil24_phy_reset to use SRST instaed.
Signed-off-by: NTejun Heo <htejun@gmail.com>

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Jeff, I didn't remove the 10ms sleep just to be on the safe side.  I
think we can live with 10ms sleep on SRST.
Signed-off-by: NJeff Garzik <jgarzik@pobox.com>