plat/arm: Fix incorrect number of reserved memory map entries

There are three calls to mmap_add_region() that always occur in
arm_setup_page_tables(), and two further calls based on whether coherent
memory is enabled, and whether SPM is enabled in BL31.

This commit adapts the ARM_BL_REGIONS definition to match the number of
calls made inside arm_setup_page_tables() so that the MAX_MMAP_REGIONS
is realigned with what is actually occurring.

Change-Id: I7adc05951abccf2cbd5c86280eb874911e6a1566
Signed-off-by: Chris Kay <chris.kay@arm.com>

include/plat/arm/common/arm_def.h

@@ -245,10 +245,16 @@
  * The number of regions like RO(code), coherent and data required by
  * different BL stages which need to be mapped in the MMU.
  */
-#if USE_COHERENT_MEM
-#define ARM_BL_REGIONS			3
+#if ENABLE_SPM && defined(IMAGE_BL31)
+# if USE_COHERENT_MEM
+#  define ARM_BL_REGIONS		5
+# else
+#  define ARM_BL_REGIONS		4
+# endif
+#elif USE_COHERENT_MEM
+# define ARM_BL_REGIONS			4
 #else
-#define ARM_BL_REGIONS			2
+# define ARM_BL_REGIONS			3
 #endif
 
 #define MAX_MMAP_REGIONS		(PLAT_ARM_MMAP_ENTRIES +	\