scsi: qla2xxx: Change debug message during driver unload

Upon driver unload, purge_mbox flag is set and the heartbeat monitor thread
detects this flag and does not send the mailbox command down to FW with a
debug message "Error detected: purge[1] eeh[0] cmd=0x0, Exiting".  This
being not a real error, change the debug message.

Cc: stable@vger.kernel.org
Signed-off-by: Saurav Kashyap <skashyap@marvell.com>
Signed-off-by: Nilesh Javali <njavali@marvell.com>
Link: https://lore.kernel.org/r/20240227164127.36465-10-njavali@marvell.com
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>