iommu/irq_remapping: Kill function irq_remapping_supported() and related code

Simplify irq_remapping code by killing irq_remapping_supported() and
related interfaces.

Joerg posted a similar patch at https://lkml.org/lkml/2014/12/15/490

,
so assume an signed-off from Joerg.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Joerg Roedel <joro@8bytes.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: iommu@lists.linux-foundation.org
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David Rientjes <rientjes@google.com>
Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Cc: Jan Beulich <JBeulich@suse.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Oren Twaig <oren@scalemp.com>
Link: http://lkml.kernel.org/r/1420615903-28253-14-git-send-email-jiang.liu@linux.intel.com


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