ARM boot: add MODE_RESERVED to MAX_NUM_FREEMEM_REG

This accounts for the ASID PD hole splitting the main memory region.

include/kernel/boot.h

@@ -20,7 +20,7 @@
  *  + 1: allow the kernel to release its own boot data region
  *  + 1: possible gap between ELF images and rootserver objects;
  *       see arm/arch_init_freemem */
-#define MAX_NUM_FREEMEM_REG (ARRAY_SIZE(avail_p_regs) + 1 + 1)
+#define MAX_NUM_FREEMEM_REG (ARRAY_SIZE(avail_p_regs) + MODE_RESERVED + 1 + 1)
 #endif
 
 /*