qla2xxx: Look up LUN for abort requests

Search through the list of pending commands on the session list to find
the command the initiator is actually aborting, so that we can pass the
correct LUN to the core TMR handling code.

(nab: Allow abort requests to work to LUN=0 with mainline target code)

Signed-off-by: Steve Hodgson <steve@purestorage.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
Cc: stable@vger.kernel.org
Signed-off-by: Nicholas Bellinger <nab@risingtidesystems.com>