bpf: fix script for generating man page on BPF helpers

The script broke on parsing function prototype for bpf_strtoul(). This
is because the last argument for the function is a pointer to an
"unsigned long". The current version of the script only accepts "const"
and "struct", but not "unsigned", at the beginning of argument types
made of several words.

One solution could be to add "unsigned" to the list, but the issue could
come up again in the future (what about "long int"?). It turns out we do
not need to have such restrictions on the words: so let's simply accept
any series of words instead.
Reported-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

scripts/bpf_helpers_doc.py

 #!/usr/bin/python3
 # SPDX-License-Identifier: GPL-2.0-only
 #
-# Copyright (C) 2018 Netronome Systems, Inc.
+# Copyright (C) 2018-2019 Netronome Systems, Inc.
 
 # In case user attempts to run with Python 2.
 from __future__ import print_function
@@ -39,7 +39,7 @@ class Helper(object):
         Break down helper function protocol into smaller chunks: return type,
         name, distincts arguments.
         """
-        arg_re = re.compile('((const )?(struct )?(\w+|...))( (\**)(\w+))?$')
+        arg_re = re.compile('((\w+ )*?(\w+|...))( (\**)(\w+))?$')
         res = {}
         proto_re = re.compile('(.+) (\**)(\w+)\(((([^,]+)(, )?){1,5})\)$')
 
@@ -54,8 +54,8 @@ class Helper(object):
             capture = arg_re.match(a)
             res['args'].append({
                 'type' : capture.group(1),
-                'star' : capture.group(6),
-                'name' : capture.group(7)
+                'star' : capture.group(5),
+                'name' : capture.group(6)
             })
 
         return res