ArmPkg/ArmExceptionLib: don't restore ESR and FAR upon exception return

ArmPkg/ArmExceptionLib: don't restore ESR and FAR upon exception return

ESR and FAR are populated by the hardware upon exception entry, and
describe the exception, not the interrupted context. So there is no point
in restoring their values before returning from the exception.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Eugene Cohen <eugene@hp.com>