ASoC: stm32: spdifrx: retry synchronization in sync state

When STM32 SPDIFRX is in sync state, allow multiple
synchro attempts, instead of exiting on first unsuccessful
trial. This is useful when spdif signal is not immediately
available on input. This also allows Pulseaudio to check
iec capture device availability when no signal is present.

Signed-off-by: Olivier Moysan <olivier.moysan@st.com>
Link: https://lore.kernel.org/r/20191011084816.14279-1-olivier.moysan@st.com


Signed-off-by: Mark Brown <broonie@kernel.org>