dynamic_debug: add #include <linux/sched.h>

This fixes a build breakage caused by
8ba6ebf583f12da32036fc0f003ab4043e54692e "Dynamic debug: Add more flags"

Cc: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

lib/dynamic_debug.c

@@ -29,6 +29,7 @@
 #include <linux/slab.h>
 #include <linux/jump_label.h>
 #include <linux/hardirq.h>
+#include <linux/sched.h>
 
 extern struct _ddebug __start___verbose[];
 extern struct _ddebug __stop___verbose[];