soundwire: cadence: make SSP interval programmable

soundwire: cadence: make SSP interval programmable

In multi-master mode, the IP will only accept SSP intervals with
integer relationships between the frame rate and the gsync frequency.

E.g for a 48kHz frame rate and 4 kHz gsync signal, the SSP interval
can only be 1, 2, 3, 4, 6, 12.

To simplify we only allow one SSP per gsync interval.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200317163329.25501-11-pierre-louis.bossart@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>