ACPI/APMT: Don't register invalid resource

Don't register a resource for the second page unless the dual-page
extension flag is actually present to say it's valid.

CC: Lorenzo Pieralisi <lpieralisi@kernel.org>
CC: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Reviewed-and-tested-by: Ilkka Koskinen <ilkka@os.amperecomputing.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Link: https://lore.kernel.org/r/63b34656e1f7b41bcb458fb6d7496e04db757e0d.1685983270.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>