dkms: use the git fetcher for the dkms source
dkms: use the git fetcher for the dkms source

The dkms v2.4.0 release archive has been deleted from the dell github
project. It is generally not a good idea to rely on github artifacts for
bitbake recipe sources, since there are no LTS guarantees.

Switch the primary dkms source URI to the git protocol, and explicitly
request the commit which corresponds to tag `v2.4.0`.

Signed-off-by: Alex Stewart <04cdb2793e4fb0120cc30d1c823099f3862701f4@ni.com>

ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt