Audio .WAV format player.

This example project uses the EFM32 CMSIS including DK BSP (board support
package) and demonstrates how to play a wav file from the SD-card.

The wav file must be named "sweet1.wav" and must be encoded with 16-bit
PCM audio sampling.

The output volume level is adjusted with kit pushbuttons PB1 and PB2.
Output level is indicated by the 14 leftmost user LEDs.
Push the AEM button on the kit until "EFM" shows in the upper right
corner of the TFT display to activate PB1 and PB2 pushbuttons.

The example can be build for using the I2S dac or onchip DAC0.
Look for #define USE_I2S near top of file wavplayer.c

It sets up access to DVK registers, and supports fat-filesystem on the
sd-card.

Board:  Silicon Labs EFM32WG-DK3850 Development Kit
Device: EFM32WG990F256
