rockchip: rk3368: increase MAX_MMAP_REGIONS

Current value is 16, count the MAP_REGION calls gets us at least 17,
so increase the max value to 20 to have a bit of a margin.
Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Change-Id: I93d0324f3d483758366e758f8f663545d365e03f

plat/rockchip/rk3368/include/platform_def.h

@@ -86,7 +86,7 @@
 #define PLAT_VIRT_ADDR_SPACE_SIZE   (1ULL << 32)
 #define PLAT_PHY_ADDR_SPACE_SIZE    (1ULL << 32)
 #define MAX_XLAT_TABLES		8
-#define MAX_MMAP_REGIONS	16
+#define MAX_MMAP_REGIONS	20
 
 /*******************************************************************************
  * Declarations and constants to access the mailboxes safely. Each mailbox is