iommufd/selftest: Fix page leaks in mock_viommu_{init,destroy}

mock_viommu_init() allocates two pages using __get_free_pages(..., 1),
but its error path and mock_viommu_destroy() only release the first page
using free_page(), leaking the second page. Use free_pages() with the
matching order instead to avoid any page leaks.

Fixes: 80478a2 ("iommufd/selftest: Add coverage for the new mmap interface")
Link: https://patch.msgid.link/r/20260312164040.457293-3-thorsten.blum@linux.dev
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Author: toblux

drivers/iommu/iommufd/selftest.c

@@ -636,7 +636,7 @@ static void mock_viommu_destroy(struct iommufd_viommu *viommu)
 	if (mock_viommu->mmap_offset)
 		iommufd_viommu_destroy_mmap(&mock_viommu->core,
 					    mock_viommu->mmap_offset);
-	free_page((unsigned long)mock_viommu->page);
+	free_pages((unsigned long)mock_viommu->page, 1);
 	mutex_destroy(&mock_viommu->queue_mutex);
 
 	/* iommufd core frees mock_viommu and viommu */
@@ -870,7 +870,7 @@ static int mock_viommu_init(struct iommufd_viommu *viommu,
 	iommufd_viommu_destroy_mmap(&mock_viommu->core,
 				    mock_viommu->mmap_offset);
 err_free_page:
-	free_page((unsigned long)mock_viommu->page);
+	free_pages((unsigned long)mock_viommu->page, 1);
 	return rc;
 }