enchilada / fajita: update to 5.9 kernel and start preparing for audio support

There aren't many functional changes in this update, the kernel has been updated to the 5.9 tag.

We add a service to manually start the ADSP as it doesn't attempt to boot again after failing to find firmware whilst in the initramfs, this will be needed for audio support in the future.

Making all remoteproc drivers modules fixes failed remoteproc boots during early init.