ALSA: line6: fix a crash in line6_hwdep_write()

The error checking here is messed up so we could end up dereferencing
-EFAULT.

Fixes: a16039cb

 ('ALSA: line6: Add hwdep interface to access the POD control messages')
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>