UEFI: Don't pass boot services regions to SetVirtualAddressMap()

We need to map boot services regions during startup in order to avoid
firmware bugs, but we shouldn't be passing those regions to
SetVirtualAddressMap(). Ensure that we're only passing regions that are
marked as being mapped at runtime.

Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>