soundwire: intel: read mclk_freq property from firmware

The BIOS provides an Intel-specific property, let's use it to avoid
hard-coded clock dividers.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20190806005522.22642-12-pierre-louis.bossart@linux.intel.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>