asoc: bolero: remove mutex_lock in bolero_runtime_suspend

There can be deadlock between __bolero_reg_read/write and
bolero_runtime_suspend. Remove the mutex_lock in
bolero_runtime_suspend to avoid deadlock.

Change-Id: I712b9f24adeddda8899b39f90291394965443163
Signed-off-by: Meng Wang <mengw@codeaurora.org>