ENGR00295423-2 ASoC: fsl_ssi: Don't set clock rate in hw_params()

ENGR00295423-2 ASoC: fsl_ssi: Don't set clock rate in hw_params()

Leaving clk_set_rate() in hw_params() is a bit dangerous when handling two
substreams. So we let set_sysclk() finish the clk_set_rate() directly.

This patch also adds spinlock to protect the baud clock configuration so
that it won't be broken during race.

Signed-off-by: Nicolin Chen <Guangyu.Chen@freescale.com>
(cherry picked from commit d3818ba35e4cbb6a3fa769eb83ceb7335b7c19e6)