ahci: Factor out PCI specifics from ahci_save_initial_config()

Make ahci_save_initial_config() a bit more generic by introducing
force_port_map and mask_port_map arguments.

Move PCI stuff into ahci_pci_save_initial_config().

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