MdePkg: remove redundant handling of EFI_IMAGE_REL_BASED_DIR64 relocations

MdePkg: remove redundant handling of EFI_IMAGE_REL_BASED_DIR64 relocations

There is AARCH64 specific code in the PE/COFF loader to handle relocations
of type EFI_IMAGE_REL_BASED_DIR64 which is dead code since this type is
handled by generic code and never handed to the AARCH64 specific routine.
So remove it.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18556 6f19259b-4bc3-4df7-8a09-765794883524