samples: drivers: i2s: add output sample

Add simple I2S output sample. This sample is verified with the RT1060
EVKB, but can be ported to any board with I2S support. It simply
demonstrates how to write I2S output data using the I2S API. The output
can be verified using a signal analyzer, if the user desires.

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>