ASoC: ssm4567: Keep TDM_BCLKS in ssm4567_set_dai_fmt

The regmap_write in ssm4567_set_dai_fmt accidentally clears the
TDM_BCLKS field which was set earlier by ssm4567_set_tdm_slot.

This patch fixes it by using regmap_update_bits with proper mask.

Signed-off-by: Ben Zhang <benzh@chromium.org>
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Anatol Pomozov <anatol.pomozov@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org