scripts/kernel-doc: Add missing close-paren in c:function directives

When kernel-doc generates a 'c:function' directive for a function
one of whose arguments is a function pointer, it fails to print
the close-paren after the argument list of the function pointer
argument. For instance:

 long work_on_cpu(int cpu, long (*fn) (void *, void * arg)

in driver-api/basics.html is missing a ')' separating the
"void *" of the 'fn' arguments from the ", void * arg" which
is an argument to work_on_cpu().

Add the missing close-paren, so that we render the prototype
correctly:

 long work_on_cpu(int cpu, long (*fn)(void *), void * arg)

(Note that Sphinx stops rendering a space between the '(fn*)' and the
'(void *)' once it gets something that's syntactically valid.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Link: https://lore.kernel.org/r/20200414143743.32677-1-peter.maydell@linaro.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

scripts/kernel-doc

@@ -853,7 +853,7 @@ sub output_function_rst(%) {
 
 	if ($type =~ m/([^\(]*\(\*)\s*\)\s*\(([^\)]*)\)/) {
 	    # pointer-to-function
-	    print $1 . $parameter . ") (" . $2;
+	    print $1 . $parameter . ") (" . $2 . ")";
 	} else {
 	    print $type . " " . $parameter;
 	}