SPM: Add missing #include statement

This header file is missing when all partitions are disabled.

Change-Id: I2de03cda9c38a107889d83315e5f2e411500e617
Signed-off-by: Håkon Øye Amundsen <haakon.amundsen@nordicsemi.no>
diff --git a/secure_fw/spm/cmsis_func/main.c b/secure_fw/spm/cmsis_func/main.c
index 259293b..14d618b 100644
--- a/secure_fw/spm/cmsis_func/main.c
+++ b/secure_fw/spm/cmsis_func/main.c
@@ -11,6 +11,7 @@
 #include "spm_func.h"
 #include "tfm_hal_defs.h"
 #include "tfm_hal_platform.h"
+#include "tfm_hal_isolation.h"
 #include "tfm_irq_list.h"
 #include "tfm_nspm.h"
 #include "tfm_spm_hal.h"