bpftool: Recognize arena map type

Teach bpftool to recognize arena map type.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20240308010812.89848-10-alexei.starovoitov@gmail.com

Author: Alexei Starovoitov

tools/bpf/bpftool/Documentation/bpftool-map.rst

@@ -55,7 +55,7 @@ MAP COMMANDS
 |		| **devmap** | **devmap_hash** | **sockmap** | **cpumap** | **xskmap** | **sockhash**
 |		| **cgroup_storage** | **reuseport_sockarray** | **percpu_cgroup_storage**
 |		| **queue** | **stack** | **sk_storage** | **struct_ops** | **ringbuf** | **inode_storage**
-|		| **task_storage** | **bloom_filter** | **user_ringbuf** | **cgrp_storage** }
+|		| **task_storage** | **bloom_filter** | **user_ringbuf** | **cgrp_storage** | **arena** }
 
 DESCRIPTION
 ===========

tools/bpf/bpftool/map.c

@@ -1463,7 +1463,7 @@ static int do_help(int argc, char **argv)
 		"                 devmap | devmap_hash | sockmap | cpumap | xskmap | sockhash |\n"
 		"                 cgroup_storage | reuseport_sockarray | percpu_cgroup_storage |\n"
 		"                 queue | stack | sk_storage | struct_ops | ringbuf | inode_storage |\n"
-		"                 task_storage | bloom_filter | user_ringbuf | cgrp_storage }\n"
+		"                 task_storage | bloom_filter | user_ringbuf | cgrp_storage | arena }\n"
 		"       " HELP_SPEC_OPTIONS " |\n"
 		"                    {-f|--bpffs} | {-n|--nomount} }\n"
 		"",