tools: bpftool: make syntax for program map update explicit in man page

Specify in the documentation that when using bpftool to update a map of
type BPF_MAP_TYPE_PROG_ARRAY, the syntax for the program used as a value
should use the "id|tag|pinned" keywords convention, as used with
"bpftool prog" commands.

Fixes: ff69c21 ("tools: bpftool: add documentation")
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

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

@@ -31,7 +31,8 @@ MAP COMMANDS
 |	**bpftool** **map help**
 |
 |	*MAP* := { **id** *MAP_ID* | **pinned** *FILE* }
-|	*VALUE* := { *BYTES* | *MAP* | *PROGRAM* }
+|	*PROG* := { **id** *PROG_ID* | **pinned** *FILE* | **tag** *PROG_TAG* }
+|	*VALUE* := { *BYTES* | *MAP* | *PROG* }
 |	*UPDATE_FLAGS* := { **any** | **exist** | **noexist** }
 
 DESCRIPTION