bpftool: Add syscall prog type

In addition to displaying the program type in bpftool prog show
this enables us to be able to query bpf_prog_type_syscall
availability through feature probe as well as see
which helpers are available in those programs (such as
bpf_sys_bpf and bpf_sys_close)

Signed-off-by: Milan Landaverde <milan@mdaverde.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20220331154555.422506-2-milan@mdaverde.com

tools/bpf/bpftool/prog.c

@@ -68,6 +68,7 @@ const char * const prog_type_name[] = {
 	[BPF_PROG_TYPE_EXT]			= "ext",
 	[BPF_PROG_TYPE_LSM]			= "lsm",
 	[BPF_PROG_TYPE_SK_LOOKUP]		= "sk_lookup",
+	[BPF_PROG_TYPE_SYSCALL]			= "syscall",
 };
 
 const size_t prog_type_name_size = ARRAY_SIZE(prog_type_name);