dm ioctl: do not leak argv if target message only contains whitespace

If 'argc' is zero we jump to the 'out:' label, but this leaks the
(unused) memory that 'dm_split_args()' allocated for 'argv' if the
string being split consisted entirely of whitespace.  Jump to the
'out_argv:' label instead to free up that memory.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Cc: stable@kernel.org
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/dm-ioctl.c

@@ -1437,7 +1437,7 @@ static int target_message(struct dm_ioctl *param, size_t param_size)
 
 	if (!argc) {
 		DMWARN("Empty message received.");
-		goto out;
+		goto out_argv;
 	}
 
 	table = dm_get_live_table(md);