openal-dec: fix missing list_devices unit for list_devices AVOption

Found-by: Ramiro
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavdevice/openal-dec.c

@@ -224,7 +224,7 @@ static const AVOption options[] = {
     {"channels", "set number of channels",     OFFSET(channels),     FF_OPT_TYPE_INT, {.dbl=2},     1, 2,      AV_OPT_FLAG_DECODING_PARAM },
     {"sample_rate", "set sample rate",         OFFSET(sample_rate),  FF_OPT_TYPE_INT, {.dbl=44100}, 1, 192000, AV_OPT_FLAG_DECODING_PARAM },
     {"sample_size", "set sample size",         OFFSET(sample_size),  FF_OPT_TYPE_INT, {.dbl=16},    8, 16,     AV_OPT_FLAG_DECODING_PARAM },
-    {"list_devices", "list available devices", OFFSET(list_devices), FF_OPT_TYPE_INT, {.dbl=0},     0, 1,      AV_OPT_FLAG_DECODING_PARAM },
+    {"list_devices", "list available devices", OFFSET(list_devices), FF_OPT_TYPE_INT, {.dbl=0},     0, 1,      AV_OPT_FLAG_DECODING_PARAM, "list_devices"  },
     {"true",  "", 0, FF_OPT_TYPE_CONST, {.dbl=1}, 0, 0, AV_OPT_FLAG_DECODING_PARAM, "list_devices" },
     {"false", "", 0, FF_OPT_TYPE_CONST, {.dbl=0}, 0, 0, AV_OPT_FLAG_DECODING_PARAM, "list_devices" },
     {NULL},