ASoC: davinci-mcasp: Set BCLK divider if McASP is BCLK master

Make BCLK divider setting implicite in hw_params call if McASP device
is the bit clock master on the audio serial bus.

Signed-off-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Mark Brown <broonie@linaro.org>