[SCSI] bnx2fc: NPIV ports go offline when interface is brought down & up

When there are 255 NPIV ports, and the interface is brought down & up, both
physical and NPIV ports are logged off and never logged back in. Since
discovery happens on single CPU, XID resources on that CPU will be limited,
which when exhausted the discovery fails. Increase the XID resource range to
ensure that the discovery completes successfully. Also ensure that
fc_exch_mgr_alloc() doesn't fail on the system that has lower number of CPUs.

Signed-off-by: Bhanu Prakash Gollapudi <bprakash@broadcom.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>