Fix: testing for mpu wrapers to be equal to 1 (#285)

diff --git a/include/mpu_wrappers.h b/include/mpu_wrappers.h
index a5c081f..6550c1e 100644
--- a/include/mpu_wrappers.h
+++ b/include/mpu_wrappers.h
@@ -29,7 +29,7 @@
 

 /* This file redefines API functions to be called through a wrapper macro, but

  * only for ports that are using the MPU. */

-#ifdef portUSING_MPU_WRAPPERS

+#if ( portUSING_MPU_WRAPPERS == 1 )

 

 /* MPU_WRAPPERS_INCLUDED_FROM_API_FILE will be defined when this file is

  * included from queue.c or task.c to prevent it from having an effect within