iommu/vt-d: Allocate IRQ remapping data structures only for all IOMMUs

IRQ remapping is only supported when all IOMMUs in the
system support it. So check if all IOMMUs in the system
support IRQ remapping before doing the allocations.

[Jiang]
1) Rebased to v3.19.
2) Remove redundant check of ecap_ir_support(iommu->ecap) in function
   intel_enable_irq_remapping().

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Tested-by: Joerg Roedel <joro@8bytes.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: iommu@lists.linux-foundation.org
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/1420615903-28253-10-git-send-email-jiang.liu@linux.intel.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>