[SCSI] qla2xxx: Correct use-after-free oops seen during EH-abort.

Hold a reference to the srb (sp) while aborting an I/O -- as the
I/O can/will complete from within the interrupt-context.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: Giridhar Malavali <giridhar.malavali@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>