plat/arm: tzc_dmc500: Add missing plat_arm.h include

This omission causes a build error as the definition for
arm_tzc_regions_info_t is needed from plat_arm.h

Change-Id: I26935ee90d3e36ab6a016ff2c4eee4413df3e4e8
Signed-off-by: Nariman Poushin <nariman.poushin@linaro.org>

plat/arm/common/arm_tzc_dmc500.c

@@ -7,6 +7,7 @@
 #include <arm_def.h>
 #include <assert.h>
 #include <debug.h>
+#include <plat_arm.h>
 #include <platform_def.h>
 #include <tzc_dmc500.h>