drivers: i2s: mcux_sai: fix PCM data format and respect CLK format

This commit fixes the following issues with the PCM data format output
by the MCUX SAI driver:

- WS signal should be only one clock cycle in length for short PCM
  format
- Word count should not be fixed to 2, except for classic I2S format
- BCLK polarity should be on falling edge for PCM long and short format

Additionally, the I2S_FMT_CLK_ constants now flip the frame and bit
clock polarity from the normal value expected for the selected I2S
format, as expected by the API.

Fixes #63041

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