Re-factor definition of TZC-400 base address

This patch replaces the `ARM_TZC_BASE` constant with `PLAT_ARM_TZC_BASE` to
support different TrustZone Controller base addresses across ARM platforms.

Change-Id: Ie4e1c7600fd7a5875323c7cc35e067de0c6ef6dd
diff --git a/plat/arm/common/arm_security.c b/plat/arm/common/arm_security.c
index 8bee4fe..990d8d4 100644
--- a/plat/arm/common/arm_security.c
+++ b/plat/arm/common/arm_security.c
@@ -47,7 +47,7 @@
 {
 	INFO("Configuring TrustZone Controller\n");
 
-	tzc_init(ARM_TZC_BASE);
+	tzc_init(PLAT_ARM_TZC_BASE);
 
 	/* Disable filters. */
 	tzc_disable_filters();