This fixes loading the regulatory database from wireless-regdb when
cfg80211 is compiled into the kernel:
cfg80211: Loading compiled-in X.509 certificates for regulatory database
Without this in the initramfs, the regulatory db fails to load the
cfg80211 is builtin and the kernel may default to using the 'global'
domain. This can cause issues in some countries.
The db + sig files are together about 5KB uncompressed, so this should
have negligible impact on the initramfs size.
[ci:skip-build]: already built successfully in CI
