There may be a race, when configuring two PWM channels, with different
prescaler values, when there's no active channel yet.
Add mutex lock to avoid concurrent access on PWM apply state.
This is also precursor patch for PWM capture support.
Signed-off-by: NFabrice Gasnier <fabrice.gasnier@st.com>
Reviewed-by: NBenjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: NThierry Reding <thierry.reding@gmail.com>