Update to systemd 247.9 from 247.3. This includes a fix which addresses
systemd-resolved resolving issues. This might help DNS resolving issues
we see in Home Assistant OS.
See also: https://github.com/systemd/systemd/issues/18917
LVM2 is not really required in the embedded use case. Opt out of
installing the standard installation which will install only dmsetup.
This requires a backported fix for the lvm2 package to not install
unnecessary systemd services.
Fixes: #1448
* Rebase patches to Buildroot 2021.02-rc3
* Update Buildroot to 2021.02-rc3
* Declare Kernel headers to be Linux version 5.10 (since they are, and new Buildroot knows about 5.10)
