iommu: simplify list initialization in iommu_create_device_direct_mappings()

Use LIST_HEAD() to declare and initialize the 'mappings' list head in
iommu_create_device_direct_mappings() instead of separate declaration and
INIT_LIST_HEAD(). This simplifies the code by combining declaration and
initialization into a single idiomatic form, improving readability without
changing functionality.

Signed-off-by: Can Peng <pengcan@kylinos.cn>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

Author: Can Peng

drivers/iommu/iommu.c

@@ -1180,12 +1180,11 @@ static int iommu_create_device_direct_mappings(struct iommu_domain *domain,
 					       struct device *dev)
 {
 	struct iommu_resv_region *entry;
-	struct list_head mappings;
+	LIST_HEAD(mappings);
 	unsigned long pg_size;
 	int ret = 0;
 
 	pg_size = domain->pgsize_bitmap ? 1UL << __ffs(domain->pgsize_bitmap) : 0;
-	INIT_LIST_HEAD(&mappings);
 
 	if (WARN_ON_ONCE(iommu_is_dma_domain(domain) && !pg_size))
 		return -EINVAL;