[SCSI] scsi_transport_sas: fix incorrect duplicate setup of max_phys

There are two setup places for max_phys in scsi_transport_sas.c; one
incorrectly places a NULL into host_attrs instead of port_attrs.  Remove it.

Reported-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>