scripts/kernel-doc: fix empty function description section

scripts/kernel-doc mishandles a function that has a multi-line function
short description and no function parameters.  The observed problem was
from drivers/scsi/scsi_netlink.c:

/**
 * scsi_netlink_init - Called by SCSI subsystem to intialize
 * 	the SCSI transport netlink interface
 *
 **/

kernel-doc treated the " * " line as a Description: section with only a
newline character in the Description contents.  This caused
output_highlight() to complain: "output_highlight got called with no
args?", plus produce a perl call stack backtrace.

The fix is just to ignore Description sections if they only contain "\n".
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

scripts/kernel-doc

@@ -2103,7 +2103,7 @@ sub process_file($) {
 		$section = $newsection;
 	    } elsif (/$doc_end/) {
 
-		if ($contents ne "") {
+		if (($contents ne "") && ($contents ne "\n")) {
 		    dump_section($file, $section, xml_escape($contents));
 		    $section = $section_default;
 		    $contents = "";