ASoC: dwc: fix support for more than two channels

There were missing break statements so everything used
TWO_CHANNEL_SUPPORT.

Also I added a return statement to silence a GCC warning:

	sound/soc/dwc/designware_i2s.c: In function ‘dw_i2s_hw_params’:
	sound/soc/dwc/designware_i2s.c:236:32: warning: ‘ch_reg’ may be
		used uninitialized in this function
		[-Wmaybe-uninitialized]

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Rajeev Kumar <rajeev-dlh.kumar@st.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>