[SCSI] mpt2sas: do not check serial_number in the abort handler

The SCSI midlayer stops all command processing when in error handling, which
means there is no chance for command reuse when the abort handler is called.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: "Moore, Eric" <Eric.Moore@lsi.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>