ASoC: sti: fix possible sleep-in-atomic

commit ce780a47

 upstream.

Change mutex and spinlock management to avoid sleep
in atomic issue.

Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Link: https://lore.kernel.org/r/20200113100400.30472-1-arnaud.pouliquen@st.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>