ASoC: atmel_ssc_dai: Don't unconditionally reset SSC on stream startup

commit cbaadf0f ("ASoC: atmel_ssc_dai: refactor the startup and
shutdown") refactored code such that the SSC is reset on every
startup; this breaks duplex audio (e.g. first start audio playback,
then start record, causing the playback to stop/hang)

Fixes: cbaadf0f (ASoC: atmel_ssc_dai: refactor the startup and shutdown)
Signed-off-by: Christoph Huber <c.huber@bct-electronic.com>
Signed-off-by: Peter Meerwald-Stadler <p.meerwald@bct-electronic.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org