[PATCH] ahci: separate out ahci_reset_controller() and ahci_init_controller()

Separate out ahci_reset_controller() and ahci_init_controller() from
ata_host_init().  These will be used by PM callbacks.  This patch
doesn't introduce any behavior change.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Zhao, Forrest <forrest.zhao@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>