app_usb_aud_xk_316: recording at 16kHz

[xross]

The PCM1865 ADC on the XK-AUDIO-316-MC doesn't support 16kHz with a 24.576MHz master clock - the highest it can use for 16kHz is 12.288MHz see table 9, page 40 of the datasheet.

Currently if a customer wants to use these lower rates they should reduce the master clock frequencies accordingly (see MCLK_441 and MCLK_48 defines). This however, will reduce the maximum sample rate supported. If this is an issue the customer could add code to dynamically change the master clock based on the sample rate.