MdeModulePkg: remove unused variable DevicePathSize

MdeModulePkg: remove unused variable DevicePathSize

Remove the unused DevicePathSize variable from EnumerateAllKeywords().
Due to our use of -Werror=unused-but-set-variable when building under GCC, the presence of DevicePathSize is breaking the build.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17448 6f19259b-4bc3-4df7-8a09-765794883524