fireworks: remove sampling_rate_descs

This array is needless as long as using sprintf() with sampling_rates.
bebob: add metering and switching sampling rate by control interface

(I forgot to add ./bebob/bebob_control.c)

NOTE: if you switch sampling rate on Firewire 1814 and ProjectMix, it will fail
because its incarnation has no information.
bebob: add check_sync() to confirm clock source for MAudio devices

MAudio devices don't tell the drivers whether to detect digital clock or word
clock inputs. The driver switch clock source at first, then check sync status
via command.

Sync status is in the end of metering data. There is 4 bytes additionally to
metering data. The 2nd lowe bytes tell it. If it's 0xff, sync is failed. If
sync is success, it's the same value as SFC of FDF in IEC 61883-6.