ArmVirtPkg: factor out Rules FDF section

ArmVirtPkg: factor out Rules FDF section

All three current ArmVirtPkg have identical [Rules] sections in their
FDF definitions, and ideally, they should remain that way. So factor
out the definitions into a separate include file, and replace the
existing definitions with !include directives.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>