ALSA: line6: Fix POD HD500 audio playback

commit cc18b2f4

 upstream.

Apparently interface 1 is control interface akin to HD500X,
setting LINE6_CAP_CONTROL and choosing it as ctrl_if fixes
audio playback on POD HD500.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200425201115.3430-1-anarsoul@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>