ide/atapi: Don't fail eject when tray is already open

MMC-5 6.40.2.6 specifies that START STOP UNIT succeeds when the drive
already has the requested state.  cmd_start_stop_unit() fails when
asked to eject while the tray is open and locked.  Fix that.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

hw/ide/atapi.c

@@ -910,7 +910,7 @@ static void cmd_start_stop_unit(IDEState *s, uint8_t* buf)
     bool loej = buf[4] & 2;     /* load on start, eject on !start */
 
     if (loej) {
-        if (!start && s->tray_locked) {
+        if (!start && !s->tray_open && s->tray_locked) {
             sense = bdrv_is_inserted(s->bs)
                 ? SENSE_NOT_READY : SENSE_ILLEGAL_REQUEST;
             ide_atapi_cmd_error(s, sense, ASC_MEDIA_REMOVAL_PREVENTED);