The JZ4780 I2S can feed either the internal audio codec or the HDMI
transmitter, but not both at the same time. This patch:
- Adds a dev.pcm.0.internal_codec sysctl node for selecting between internal and external codec
- Changes playback sample rate from 96 kHz to 48 kHz for HDMI compatibility
- Enables i2s clock on codec access
Reviewed by: br
Differential Revision: https://reviews.freebsd.org/D8960