Add a kernel parameter to allow coefficients to be exposed as ALSA controls.
When the CS35L41 loads its firmware, it has a number of controls to
affect its behaviour. Currently, these controls are exposed as ALSA
Controls by default.
However, nothing in userspace currently uses them, and is unlikely to
do so in the future, therefore we don't need to create ASLA controls
for them.
These controls can be useful for debug, so we can add a kernel
parameter to re-enable them if necessary.
Disabling these controls would prevent userspace from trying to read
these controls when the CS35L41 is hibernating, which ordinarily
would result in an error message.