scsi: arcmsr: Configure the default command timeout value

Allow configuring the default command timeout value for devices attached to
arcmsr controllers.

Link: https://lore.kernel.org/r/27c0cda7fd103f05021adaf67490e9298ed5cc3f.camel@areca.com.tw


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