Make the Level Meter check compatible with alsa-sim.c

Rather than retrieving the firmware version in alsa_scan_cards(), use
get_elem_by_name() to check if the control is present.

Update alsa-sim.c alsa_config_to_new_elem() to read iface=CARD
controls.

src/alsa.h

@@ -145,7 +145,6 @@ struct alsa_card {
   char               *name;
   snd_ctl_t          *handle;
   struct pollfd       pfd;
-  int                 firmware_version;
   GArray             *elems;
   struct alsa_elem   *sample_capture_elem;
   struct alsa_elem   *level_meter_elem;