Add the ability to read a SAS device's Target Port NAA designator

sys/cam/scsi/scsi_all.h
sys/cam/scsi/scsi_all.c
Add the scsi_devid_is_port_naa helper function

Reviewed by: ken
MFC after: 4 weeks
Sponsored by: Spectra Logic Corp
Differential Revision: https://reviews.freebsd.org/D5975