ArmPkg/ArmExceptionLib: Add implementation of new API

This patch add implementation of following new API introduced into
CpuExceptionHandlerLib. Since this lib hasn't support Stack Guard
and stack switch, the new method just calls original
InitializeCpuExceptionHandlers.

  EFI_STATUS
  EFIAPI
  InitializeCpuExceptionHandlersEx (
    IN EFI_VECTOR_HANDOFF_INFO            *VectorInfo OPTIONAL,
    IN CPU_EXCEPTION_INIT_DATA            *InitDataEx OPTIONAL
    );

Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Suggested-by: Ayellet Wolman <ayellet.wolman@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
Reviewed-by: Jeff Fan <vanjeff_919@hotmail.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>