ACPI/IORT: Make iort_iommu_msi_get_resv_regions() return void

ACPI/IORT: Make iort_iommu_msi_get_resv_regions() return void

At present iort_iommu_msi_get_resv_regions() returns the number of
MSI reserved regions on success and there are no users for this.
The reserved region list will get populated anyway for platforms
that require the HW MSI region reservation. Hence, change the
function to return void instead.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Steven Price <steven.price@arm.com>
Tested-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Reviewed-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/20220615101044.1972-3-shameerali.kolothum.thodi@huawei.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>