ide: fix TRIM with empty range entry

ATA-ACS-3 says "If the two byte range length is zero, then the LBA
Range Entry shall be discarded as padding."  iovecs are used as if
they are linearized, so it is incorrect to discard the rest of
this iovec.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

hw/ide/core.c

@@ -374,7 +374,7 @@ BlockDriverAIOCB *ide_issue_trim(BlockDriverState *bs,
             uint16_t count = entry >> 48;
 
             if (count == 0) {
-                break;
+                continue;
             }
 
             ret = bdrv_discard(bs, sector, count);