[PATCH] libata: separate out and export sata_port_hardreset()

Separate out sata_port_hardreset() from sata_std_hardreset().  This
will be used by LLD hardreset implementation and later by PMP.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>