ALSA: bebob: Fix a missing to unlock mutex in error handling case

ALSA: bebob: Fix a missing to unlock mutex in error handling case

In error handling case, special_clk_ctl_put() returns without unlock_mutex(),
therefore the mutex is still locked. This commit moves mutex_lock() after
the error handling case.

This commit is my solution for this post.

[PATCH -next] ALSA: bebob: Fix missing unlock on error in special_clk_ctl_put()
https://lkml.org/lkml/2014/7/20/12

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>