ALSA: bebob: code refactoring for stream format detection

ALSA bebob driver scans supported formats of packet for each direction
when probing the target device. Some helper functions are used for the
scanning, however its implementation is not necessarily irredundant.

This commit refactors the helper functions to remove redundant codes.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20210321032831.340278-2-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Iwai <tiwai@suse.de>