dynamic_debug: reduce lineno field to a saner 18 bits

lineno:24 allows files with 4 million lines, an insane file-size, even
for never-to-get-in-tree machine generated code.  Reduce this to 18
bits, which still allows 256k lines.  This is still insanely big, but
its not raving mad.

Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

include/linux/dynamic_debug.h

@@ -15,7 +15,7 @@ struct _ddebug {
 	const char *function;
 	const char *filename;
 	const char *format;
-	unsigned int lineno:24;
+	unsigned int lineno:18;
 	/*
  	 * The flags field controls the behaviour at the callsite.
  	 * The bits here are changed dynamically when the user