IB/srp: Fix srp_abort()

Before commit e494f6a7

 ("[SCSI] improved eh timeout handler") it
did not really matter whether or not abort handlers like srp_abort()
called .scsi_done() when returning another value than SUCCESS. Since
that commit however this matters. Hence only call .scsi_done() when
returning SUCCESS.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>