roms/efirom, tests/uefi-test-tools: update edk2's own submodules first

In edk2 commit 06033f5abad3 ("BaseTools: Make brotli a submodule",
2020-04-16), part of edk2-stable202005, the Brotli compressor /
decompressor source code that edk2 had flattened into BaseTools was
replaced with a git submodule.

This means we have to initialize edk2's own submodules before building
BaseTools not just in "roms/Makefile.edk2", but in "roms/Makefile" (for
the sake of the "efirom" target) and "tests/uefi-test-tools/Makefile" as
well.

Right now this patch is effectively a no-op; it will become meaningful
after we move the edk2 submodule to edk2-stable202008.

Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugs.launchpad.net/qemu/+bug/1852196


Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200908072939.30178-3-lersek@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>