scsi: arcmsr: Rename arcmsr_free_mu to arcmsr_free_io_queue

From Ching Huang <ching2048@areca.com.tw>

Rename arcmsr_free_mu to arcmsr_free_io_queue

Signed-off-by: Ching Huang <ching2048@areca.com.tw>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>