temporary work-around for not being able to read sysclk from dts for ac10x

The "sysclk = 24000000" value is supposed to come from the "clock-frequency"
field of ac108_mclk / ac10x_mclk, but somehow it isn't on 5.4 (vs 4.19). This
is a temporary work-around. For some strange unknown reasons, this affects
only the square 4-mic device, but not the linear 4-mic nor the 6-mics device.
The other two devices have two ac108's, and seem to work fine without it.

In v4.19:
seeed_voice_card_probe [snd_soc_seeed_voicecard]
 -> devm_snd_soc_register_card [snd_soc_core]
 -> snd_soc_register_card [snd_soc_core]
 -> seeed_voice_card_dai_init [snd_soc_seeed_voicecard]
 -> asoc_simple_card_init_dai [snd_soc_simple_card_utils]
 -> snd_soc_dai_set_sysclk [snd_soc_core]
 -> ac108_set_sysclk [snd_soc_ac108]

In 5.4:
seeed_voice_card_probe [snd_soc_seeed_voicecard]
 -> devm_snd_soc_register_card [snd_soc_core]
 -> snd_soc_register_card [snd_soc_core]
 -> snd_soc_instantiate_card [snd_soc_core]
 -> seeed_voice_card_dai_init [snd_soc_seeed_voicecard]
 -> asoc_simple_init_dai.part.0 [snd_soc_seeed_voicecard]
 -> snd_soc_dai_set_sysclk [snd_soc_core]
 -> ac108_set_sysclk [snd_soc_ac108]

Which results in the "ac108_set_sysclk  :24000000" kernel message.

Note the extra snd_soc_instantiate_card(), and the copied/renamed
asoc_simple_init_dai() - it became static and not-available to other drivers
in v5.x.

See https://github.com/respeaker/seeed-voicecard/issues/246

seeed-voicecard.c

@@ -457,6 +457,8 @@ static int seeed_voice_card_dai_link_of(struct device_node *node,
 	#else
 	ret = asoc_simple_parse_clk_codec(dev, codec, dai_link, codec_dai);
 	#endif
+	if (!strncmp(dai_link->codecs->dai_name, "ac10", 4))
+		codec_dai->sysclk = 24000000;
 	if (ret < 0)
 		goto dai_link_of_err;