clk: fsl-sai: new driver

With this driver it is possible to use the BCLK pin of the SAI module as
a generic clock output. This is esp. useful if you want to drive a clock
to an audio codec. Because the output only allows integer divider values
the audio codec needs an integrated PLL.

Signed-off-by: Michael Walle <michael@walle.cc>
Link: https://lkml.kernel.org/r/20200102231101.11834-3-michael@walle.cc


Signed-off-by: Stephen Boyd <sboyd@kernel.org>