intel-iommu: fix return value of iommu_unmap() API

intel-iommu: fix return value of iommu_unmap() API

commit 292827cb164ad00cc7689a21283b1261c0b6daed upstream.

iommu_unmap() API expects IOMMU drivers to return the actual page order
of the address being unmapped.  Previous code was just returning page
order passed in from the caller.  This patch fixes this problem.

Signed-off-by: Allen Kay <allen.m.kay@intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Youquan Song <youquan.song@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>