ASoC: hdmi-codec: Use different name for playback streams

Currently the hdmi i2s playback stream and hdmi spdif playback stream
are using the same name. So when they are enabled at the same time,
kernel will print this warning:

[    2.201835] hdmi-audio-codec hdmi-audio-codec.1.auto: ASoC: Failed to
create Playback debugfs file

Assign different names to them to avoid that.

Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Mark Brown <broonie@kernel.org>