ASoC: atmel_ssc_dai: refactor the startup and shutdown

In startup function, enable ssc clock and in shutdown function,
disable clock. And also remove disable ssc in shutdown function,
as ssc is disabled in prepare function.

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --cc sound/soc/atmel/atmel_ssc_dai.c
Simple merge