iommu: Introduce a callback to struct iommu_resv_region

iommu: Introduce a callback to struct iommu_resv_region

A callback is introduced to struct iommu_resv_region to free memory
allocations associated with the reserved region. This will be useful
when we introduce support for IORT RMR based reserved regions.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Steven Price <steven.price@arm.com>
Tested-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Tested-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Acked-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/20220615101044.1972-2-shameerali.kolothum.thodi@huawei.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>