make-release: pull in edk2 submodules so we can build it from tarballs

make-release: pull in edk2 submodules so we can build it from tarballs

The `make efi` target added by 536d2173 is built from the roms/edk2
submodule, which in turn relies on additional submodules nested under
roms/edk2.

The make-release script currently only pulls in top-level submodules,
so these nested submodules are missing in the resulting tarball.

We could try to address this situation more generally by recursively
pulling in all submodules, but this doesn't necessarily ensure the
end-result will build properly (this case also required other changes).

Additionally, due to the nature of submodules, we may not always have
control over how these sorts of things are dealt with, so for now we
continue to handle it on a case-by-case in the make-release script.

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Bruce Rogers <brogers@suse.com>
Cc: qemu-stable@nongnu.org # v4.1.0
Reported-by: Bruce Rogers <brogers@suse.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Message-Id: <20190912231202.12327-2-mdroth@linux.vnet.ibm.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>