ASoC: dwc: Disallow building designware_pcm as a module

Designware PCM is an extension to Designware I2S and they are dependent
on each other. For this reason, make Designware PCM a boolean which will
compile with Desigwnare I2S module. The name of the module is not changed
but the name of the files need to be changed.

Also, without this commit we get errors when probbing designware_i2s module
because of unspecified license:

designware_pcm: module license 'unspecified' taints kernel.
Disabling lock debugging due to kernel taint
designware_pcm: Unknown symbol __rcu_read_lock (err 0)
designware_pcm: Unknown symbol devm_snd_soc_register_platform (err 0)
designware_pcm: Unknown symbol synchronize_rcu (err 0)
designware_pcm: Unknown symbol __rcu_read_unlock (err 0)
designware_pcm: Unknown symbol snd_soc_set_runtime_hwparams (err 0)

So, this is really needed as a fix.

Fixes: 79361b2b

 ("ASoC: dwc: Add PIO PCM extension")
Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: Mark Brown <broonie@kernel.org>