bug#53554: linux-libre 5.16 doesn't work with our default-initrd-modules

[Leo Famulari]

As described in the patch ticket for linux-libre 5.16 [0], this kernel
series doesn't work by default on Guix System.

To paraphrase my request for help from that ticket:

When I test this package with `guix system vm --no-grafts
doc/os-config-bare-bones.texi`, Guix fails to build the VM with this
error message:

------
gnu/build/linux-modules.scm:257:5: kernel module not found 
"framebuffer_coreboot" 
"/gnu/store/fffl383am3si0f1brb5azyqcnrnp5rj3-linux-libre-5.16/lib/modules"
------

We added a dependency on this module in commit bc09e7ab569, "gnu:
linux-libre: Support the Coreboot framebuffer." [1]

Among other things, that commit sets
"CONFIG_GOOGLE_FRAMEBUFFER_COREBOOT=m" and adds 'framebuffer_coreboot'
to ((gnu system linux-initrd) default-initrd-modules).

But, this config option is not offered to me when creating the config
files, and so the module is not built.

Any advice? It would be great if we didn't have to manually edit the
configs each time we add a new kernel series.

[0] https://issues.guix.gnu.org/53356#0
[1] 
https://git.savannah.gnu.org/cgit/guix.git/commit/?id=bc09e7ab569d5306ce99c5525150695c9d539ef0