mips: migrate core kernel file from module.h --> export.h

These files are not modules, but were including module.h only for
EXPORT_SYMBOL and/or THIS_MODULE.  Now that we have the lightweight
export.h, use it in these kinds of cases.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/arch/mips/kernel/stacktrace.c b/arch/mips/kernel/stacktrace.c
index d52ff77..1ba775d 100644
--- a/arch/mips/kernel/stacktrace.c
+++ b/arch/mips/kernel/stacktrace.c
@@ -5,7 +5,7 @@
  */
 #include <linux/sched.h>
 #include <linux/stacktrace.h>
-#include <linux/module.h>
+#include <linux/export.h>
 #include <asm/stacktrace.h>
 
 /*