scripts: kernel_doc: fixup reporting of function identifiers

When function description includes brackets after the function name as
suggested by Documentation/doc-guide/kernel-doc, the kernel-doc script
omits the function name from "Scanning doc for" report.
Extending match for identifier name with optional brackets fixes this
issue.
Signed-off-by: NMike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

scripts/kernel-doc

@@ -1873,7 +1873,7 @@ sub process_file($) {
 	    }
 	    elsif (/$doc_decl/o) {
 		$identifier = $1;
-		if (/\s*([\w\s]+?)\s*-/) {
+		if (/\s*([\w\s]+?)(\(\))?\s*-/) {
 		    $identifier = $1;
 		}