ASoC: soc-compress: prevent the potentially use of null pointer

In the Linux kernel, the following vulnerability has been resolved:

ASoC: soc-compress: prevent the potentially use of null pointer

There is one call trace that snd_soc_register_card()

->snd_soc_bind_card()->soc_init_pcm_runtime()

->snd_soc_dai_compress_new()->snd_soc_new_compress().

In the trace the 'codec_dai' transfers from card->dai_link,

and we can see from the snd_soc_add_pcm_runtime() in

snd_soc_bind_card() that, if value of card->dai_link->num_codecs

is 0, then 'codec_dai' could be null pointer caused

by index out of bound in 'asoc_rtd_to_codec(rtd, 0)'.

And snd_soc_register_card() is called by various platforms.

Therefore, it is better to add the check in the case of misusing.

And because 'cpu_dai' has already checked in soc_init_pcm_runtime(),

there is no need to check again.

Adding the check as follow, then if 'codec_dai' is null,

snd_soc_new_compress() will not pass through the check

'if (playback + capture != 1)', avoiding the leftover use of

'codec_dai'.