scsi: qla2xxx: Serialize fc_port alloc in N2N

scsi: qla2xxx: Serialize fc_port alloc in N2N

For N2N, fc_port struct is created during report id acquisition.  At
later time, the loop resync (fabric, n2n, loop) would trigger the rest
of the login using the created fc_port struct.  The loop resync logic
can trigger another fc_port allocation if the 1st allocation was not
able to execute.  This patch prevents the 2nd allocation trigger.

Link: https://lore.kernel.org/r/20200226224022.24518-15-hmadhani@marvell.com
Signed-off-by: Himanshu Madhani <hmadhani@marvell.com>
Signed-off-by: Quinn Tran <qutran@marvell.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>