ASOC: dwc: Fix 16-bit audio handling

ASOC: dwc: Fix 16-bit audio handling

IMO the Synopsys datasheet could be clearer in this area, but it seems
that the DMA data ports (DMATX and DMARX) expect left and right samples
in alternate writes; if a stereo pair is pushed in a single 32-bit
write, the upper half is ignored, leading to double speed audio with a
confused stereo image. Make sure the necessary changes happen by
updating the DMA configuration data in the hw_params method.

The set_bclk_ratio change was made at a time when it looked like it
could be causing an error, but I think the division of responsibilities
is clearer this way (and the kernel log clearer without the info-level
message).

Signed-off-by: Phil Elwell <phil@raspberrypi.com>