fix(docker/edk2): shallow submodules for edk2-stable202008

- for some reason edk2-stable202008 fails to clone all of the git
  submodules when shallow recursive init is used
- so to fix this we need to add IF ELSE statement to not use shallow
  clone on git submodules for edk2-stable202008
- shame on you ekd2, shame on you

Signed-off-by: AtomicFS <vojtech.vesely@9elements.com>

docker/edk2/Dockerfile

@@ -147,7 +147,11 @@ RUN mkdir Edk2 && \
     git remote add origin https://github.com/tianocore/edk2.git && \
     git fetch --depth 1 origin "${EDK2_VERSION_COMMIT}" && \
     git checkout "${EDK2_VERSION_COMMIT}" && \
-    git submodule update --init --recursive --depth 1 && \
+    if [ "${EDK2_VERSION}" = 'edk2-stable202008' ]; then \
+        git submodule update --init --recursive; \
+    else \
+        git submodule update --init --recursive --depth 1; \
+    fi && \
     if [ "${TARGETARCH}" = 'amd64' ]; then \
         make -C BaseTools/ -j "$(nproc)"; \
     fi;