esp: store lun coming from the MESSAGE OUT phase
The LUN is selected with an IDENTIFY message, and persists
until the next message out phase. Instead of passing it to
do_busid_cmd, store it in ESPState. Because do_cmd can simply
skip the message out phase if cmdfifo_cdb_offset is zero, it
can now be used for the S without ATN cases as well.
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>