device-generic-x86_64: install all linux-firmware by default

This installs all linux-firmware by default (using pmb_recommends) in a way that allows for users to remove extraneous fw if they want.

The testing I did:

• ✅ new install includes all fw
• ✅ can remove fw that's not required by the device package
• ✅ upgrade existing install works (!4794 (11450e8b, comment 1777301950))