bebob: Fix failure to detect source of clock for Terratec Phase 88

This patch fixes a failure to open PCM device with -ENOSYS in
Terratec Phase 88.

Terratec Phase 88 has two Selector Function Blocks of AVC Audio subunit
to switch source of clock. One is to switch internal/external for the
source and another is to switch word/spdif for the external clock.

The IDs for these Selector Function Blocks are 9 and 8. But in current
implementation they're 0 and 0.

Reported-by: András Murányi <muranyia@gmail.com>
Tested-by: András Murányi <muranyia@gmail.com>
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>