[SCSI] libfc: prepare to split off struct fc_rport_priv from fc_rport_libfc_priv

While the I/O and LLD interfaces use fc_rport_libfc_priv, the
disc and rport interfaces will use fc_rport_priv, which will
be separately allocated.

Change the disc and rport usage of fc_rport_libfc_priv to fc_rport_priv.

Use #define temporarily to make both names equivalent until a
subsequent patch splits them.

Signed-off-by: Joe Eykholt <jeykholt@cisco.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>