[BUG] scsi/fcoe: Sleep-in-atomic bugs in fcoe driver

[Jia-Ju Bai <baijiaju1990@xxxxxxx>]

According to fcoe_ctlr.c, the driver may sleep under a RCU lock,
and the function call paths are:
fcoe_ctlr_disc_stop_locked (acquire the RCU lock)
  fc_rport_logoff
    mutex_lock --> may sleep

fcoe_ctlr_vn_disc
  fc_rport_login
    mutex_lock --> may sleep

fcoe_ctlr_vn_age
  fc_rport_logoff
    mutex_lock --> may sleep

These bugs are found by my static analysis tool and my code review.

Thanks,
Jia-Ju Bai