drivers: audio: tlv320dac310x: Explicitly set GPIO_DIR_OUT

As a precursor to the new GPIO API in which GPIO_DIR_OUT isn't a dts
flag move setting of GPIO_DIR_OUT from the dts to explicitly in the
code.  We remove setting the flag in intel_s1000_crb.dts as part of this
cleanup.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>