ASoC: fsl_sai: Set SAI Channel Mode to Output Mode

From SAI datasheet:

CHMOD, configures if transmit data pins are configured for TDM mode
or Output mode.
	* (0) TDM mode, transmit data pins are tri-stated when slots are
	masked or channels are disabled.
	* (1) Output mode, transmit data pins are never tri-stated and
	will output zero when slots are masked or channels are disabled.

When data pins are tri-stated, there is noise on some channels
when FS clock value is high and data is read while fsclk is
transitioning from high to low.

Fix this by setting CHMOD to Output Mode so that pins will output zero
when slots are masked or channels are disabled.

Cc: NXP Linux Team <linux-imx@nxp.com>
Signed-off-by: Cosmin-Gabriel Samoila <cosmin.samoila@nxp.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>