sunxi-hdmiaudio: Enable 32-bit audio

The original modifications for this patch originate from some custom
changes made to the 3.3 Android kernel by huangxin at allwinnertech.com.

The A10/A20 DMA engine for HDMI audio only supports 16 or 32-bit
transfers. The documentation says 16, 20, and 24 bits, but I have not
been able to get 24-bit audio, ether 3-bytes (PCM_FMTBIT_24_3LE) or
4-bytes (PCM_FMTBIT_24_LE) to work.

This patch removes the non-working PCM formats, PCM_FMTBIT_S18_3LE
and PCM_FMTBIT_S20_3LE, and PCM_FMTBIT_S24_LE and adds suppor for
32-bit HDMI audio (PCM_FMTBIT_S32_LE).  It's possible that other 32-bit
formats, like PCM_FMTBIT_U32_LE or PCM_FMTBIT_FLOAT_LE might work, but
couldn't be tested.

This patch was tested with 24-bit and 32-bit .wav files and the ALSA
"plughw" plugin (for upconverting the 24-bit audio files to 23-bits)
with aplay -v to verify that the target format was S32_LE.

Signed-off-by: Patrick Wood <patrickhwood@gmail.com>
Sun8i changes to system header