ALSA: bebob: link the order of establishing connections and Syt-match clock mode

Originally BeBeB ASICs and firmware supports clock mode to synchronizing
to syt field of received isoc packet. This mode is known as 'SYT Match'
slightly described in IEC 61883-6 (but no detail mechanisms). In this
mode, drivers can control sampling clock in device. Driver for Windows
and macOS uses this feature to perform synchronization for devices
on the same bus.

In this mode, a plug of Music subunit for synchronization is connected
to a plug of isoc unit for incoming packet streaming, then the order to
establish connections is INPUT_PLUG first, OUTPUT_PLUG second.

This commit implements the above.

Actually each device works with its own clock for sampling, therefore
the original design is hardly implemented to vendor's products.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20191101131323.17300-4-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>