genksyms: restrict direct-declarator to take one parameter-type-list

Similar to the previous commit, this change makes the parser logic a
little more accurate.

Currently, genksyms accepts the following invalid code:

    struct foo {
            int (*callback)(int)(int)(int);
    };

A direct-declarator should not recursively absorb multiple
( parameter-type-list ) constructs.

In the example above, (*callback) should be followed by at most one
(int).

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Nicolas Schier <n.schier@avm.de>

Author: masahir0y

scripts/genksyms/parse.y

@@ -331,12 +331,16 @@ nested_declarator:
 	;
 
 direct_nested_declarator:
-	IDENT	{ $$ = $1; dont_want_type_specifier = false; }
-	| direct_nested_declarator '(' parameter_declaration_clause ')'
+	direct_nested_declarator1
+	| direct_nested_declarator1 '(' parameter_declaration_clause ')'
 		{ $$ = $4; }
-	| direct_nested_declarator '(' error ')'
+	;
+
+direct_nested_declarator1:
+	IDENT	{ $$ = $1; dont_want_type_specifier = false; }
+	| direct_nested_declarator1 '(' error ')'
 		{ $$ = $4; }
-	| direct_nested_declarator BRACKET_PHRASE
+	| direct_nested_declarator1 BRACKET_PHRASE
 		{ $$ = $2; }
 	| '(' nested_declarator ')'
 		{ $$ = $3; }