tracing, Text Edit Lock: Fix one sparse warning in kernel/extable.c

Impact: cleanup.

The global mutex text_mutex if declared in linux/memory.h, so
this file needs to be included into kernel/extable.c, where the
same mutex is defined. This fixes the following sparse warning:

 kernel/extable.c:32:1: warning: symbol 'text_mutex' was not declared.
 Should it be static?
Signed-off-by: Dmitri Vorobiev <dmitri.vorobiev@movial.com>
LKML-Reference: <1237741871-5827-3-git-send-email-dmitri.vorobiev@movial.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/extable.c

@@ -16,6 +16,7 @@
     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
 #include <linux/ftrace.h>
+#include <linux/memory.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/init.h>