{ASoC,media}: constify snd_soc_component_driver

Merge series from Javier Carrasco <javier.carrasco.cruz@gmail.com>:

Declare `snd_soc_component_driver` as const to move their declarations
to read-only sections for the drivers that do not modify the struct
after its declaration.

Apart from a single case under media/, the affected drivers are members
of the ASoC subsystem.