Currently, tags are fetched as just a name, which works but means they're not
seen as tags by git commands like git describe. Instead, fetch them as refs/tags/XXX
which means such commands then work correctly.
(Bitbake rev: c1f30ad61f5e55beb377451887bbbc5cb569f2e5)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>