bpf, verifier: Use fallthrough pseudo-keyword

Replace /* fallthrough */ comments with the new pseudo-keyword
macro fallthrough [1].

  [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through

Signed-off-by: Gustavo A. R. Silva <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/bpf/20201002234217.GA12280@embeddedor

Author: GustavoARSilva

kernel/bpf/verifier.c

@@ -2673,7 +2673,7 @@ static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
 	case BPF_PROG_TYPE_CGROUP_SKB:
 		if (t == BPF_WRITE)
 			return false;
-		/* fallthrough */
+		fallthrough;
 
 	/* Program types with direct read + write access go here! */
 	case BPF_PROG_TYPE_SCHED_CLS:
@@ -5475,7 +5475,7 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		/* smin_val represents the known value */
 		if (known && smin_val == 0 && opcode == BPF_ADD)
 			break;
-		/* fall-through */
+		fallthrough;
 	case PTR_TO_PACKET_END:
 	case PTR_TO_SOCKET:
 	case PTR_TO_SOCKET_OR_NULL: