bpf: minor cleanups in helpers

Some minor misc cleanups, f.e. use sizeof(__u32) instead of hardcoding
and in __bpf_skb_max_len(), I missed that we always have skb->dev valid
anyway, so we can drop the unneeded test for dev; also few more other
misc bits addressed here.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 1ea3afb..6df73bd 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -126,7 +126,7 @@
 {
 	struct task_struct *task = current;
 
-	if (!task)
+	if (unlikely(!task))
 		return -EINVAL;
 
 	return (u64) task->tgid << 32 | task->pid;
@@ -144,12 +144,12 @@
 	kuid_t uid;
 	kgid_t gid;
 
-	if (!task)
+	if (unlikely(!task))
 		return -EINVAL;
 
 	current_uid_gid(&uid, &gid);
 	return (u64) from_kgid(&init_user_ns, gid) << 32 |
-		from_kuid(&init_user_ns, uid);
+		     from_kuid(&init_user_ns, uid);
 }
 
 const struct bpf_func_proto bpf_get_current_uid_gid_proto = {