[SCSI] mpt2sas: Set the phy identifier of the end device to the phy number of the parent device it is linked to

The phy_identifier inside the routine _transport_set_identify()
is set to sas_device_page_zero->PhyNum. This returns the
phy number of the parent device this device is linked to.
Signed-off-by: NNagalakshmi Nandigama <nagalakshmi.nandigama@lsi.com>
Signed-off-by: NJames Bottomley <JBottomley@Parallels.com>