swiotlb: drop pointless static qualifier in swiotlb_create_debugfs()

There is no need to have the 'struct dentry *d_swiotlb_usage' variable
static since new value always be assigned before use it.
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

kernel/dma/swiotlb.c

@@ -682,7 +682,7 @@ swiotlb_dma_supported(struct device *hwdev, u64 mask)
 
 static int __init swiotlb_create_debugfs(void)
 {
-	static struct dentry *d_swiotlb_usage;
+	struct dentry *d_swiotlb_usage;
 	struct dentry *ent;
 
 	d_swiotlb_usage = debugfs_create_dir("swiotlb", NULL);