edk2: get version + date from git submodule

edk2: get version + date from git submodule

Turned out hard-coding version and date in the Makefile wasn't a bright
idea.  Updating it on edk2 updates is easily forgotten.  Fetch the info
from git instead.  Store in edk2-version, so this can be committed to
the repo and is present in tarballs too.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-ID: <20240327102448.61877-2-kraxel@redhat.com>
(cherry picked from commit 6539c73dccfa8fff1f83d40f1c4477a233876071)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>