sata_fsl: Split hard and soft reset

Split sata_fsl_softreset() into hard and soft resets to make
error-handling more efficient & device and PMP detection more
reliable.

Also includes fix for PMP support, driver tested with Sil3726,
Sil4726 & Exar PMP controllers.

[AV: Also fixes resuming from deep sleep on MPC8315 CPUs]

Signed-off-by: Jiang Yutang <b14898@freescale.com>
Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>