Update edk2 headers to stable202005

Update edk2 headers to stable202005

We use these to compile libefivar. The particular motivation for this update is
the inclusion of the RISC-V machine definitions that allow us to build the
library on the platform. This support could easily have been submitted as a
small local diff, but the timing of the release coincided with this work, and
it has been over 3 years since these sources were initially imported.

Note that this comes with a license change from regular BSD 2-clause to the
BSD+Patent license. This has been approved by core@ for this particular
project [1].

As with the original import, we retain only the subset of headers that we
actually need to build libefivar. I adapted imp@'s process slightly for this
update:

    # Generate list of the headers needed to build
    cp -r ../vendor/edk2/dist/MdePkg/Include sys/contrib/edk2
    cd lib/libefivar
    make
    pushd `make -V .OBJDIR`
    cat .depend*.o | grep sys/contrib | cut -d' ' -f 3 |
        sort -u | sed -e 's=/full/path/sys/contrib/edk2/==' > /tmp/xxx
    popd

    # Merge the needed files
    cd ../../sys/contrib/edk2
    svn revert -R .
    for i in `cat /tmp/xxx`; do
        svn merge -c VendorRevision svn+ssh://repo.freebsd.org/base/vendor/edk2/dist/MdePkg/$i $i
    done
    svn merge -c VendorRevision svn+ssh://repo.freebsd.org/base/vendor/edk2/dist/MdePkg/MdePkg.dec MdePkg.dec

[1] https://www.freebsd.org/internal/software-license.html