ASoC: atmel: atmel-classd: Re-add dai_link->platform to fix card init

The removed dai_link->platform component cause a fail which
is exposed at runtime. (ex: when a sound tool is used)
This patch re-adds the dai_link->platform component to have
a full card registered.

Before this patch:
:~$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: CLASSD [CLASSD], device 0: CLASSD PCM snd-soc-dummy-dai-0 []
    Subdevices: 1/1
    Subdevice #0: subdevice #0

:~$ speaker-test -t sine
speaker-test 1.2.6
Playback device is default
Stream parameters are 48000Hz, S16_LE, 1 channels
Sine wave rate is 440.0000Hz
Playback open error: -22,Invalid argument

After this patch which restores the platform component:
:~$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: CLASSD [CLASSD], device 0: CLASSD PCM snd-soc-dummy-dai-0
						[CLASSD PCM snd-soc-dummy-dai-0]
    Subdevices: 1/1
    Subdevice #0: subdevice #0
-> Resolve the playback error.

Fixes: 2f650f87

 ("ASoC: atmel: remove unnecessary dai_link->platform")
Signed-off-by: Andrei Simion <andrei.simion@microchip.com>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://msgid.link/r/20240604101030.237792-1-andrei.simion@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>