[SCSI] qla2xxx: Read capture firmware dump on mailbox timeout for ISP8044 and ISP82XX.

Allow for the capture of a firmware dump but have a sysfs node
(allow_cna_fw_dump) to allow the feature to be enabled/disabled dynamically.

The default is off.

Signed-off-by: Chad Dupuis <chad.dupuis@qlogic.com>
Signed-off-by: Saurav Kashyap <saurav.kashyap@qlogic.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>