drivers: i2s: apply new data size for DMA interface
drivers: i2s: apply new data size for DMA interface

the old DMA driver used to use 1 to stand for 16 bits, while the
new driver uses 2 to stand for 16 bits, which means the
'source_data_size' and the 'dest_data_size' should be 2.

Signed-off-by: Song Qiang <c598b3ff423ba743d91ae7caa6428138a985a8a3@gmail.com>

nashif/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr