x64, x2apic/intr-remap: Fix the need for RMRR in the DMA-remapping detection

Presence of RMRR structures is not compulsory for enabling DMA-remapping.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Yong Y Wang <yong.y.wang@intel.com>
Cc: Yong Y Wang <yong.y.wang@intel.com>
Cc: akpm@linux-foundation.org
Cc: arjan@linux.intel.com
Cc: andi@firstfloor.org
Cc: ebiederm@xmission.com
Cc: jbarnes@virtuousgeek.org
Cc: steiner@sgi.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>