ASoC: ti: davinci-mcasp: Support for auxclk-fs-ratio

When McASP is bus master and it's AUXCLK clock is not static, but it is
a multiple of the frame sync the constraint rules should take it account
when validating possible stream formats.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>