powerpc: Removed duplicated include in stacktrace.c

Removed duplicated include file <linux/module.h> in
arch/powerpc/kernel/stacktrace.c.
Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/stacktrace.c

@@ -13,7 +13,6 @@
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/stacktrace.h>
-#include <linux/module.h>
 #include <asm/ptrace.h>
 #include <asm/processor.h>