PSCI: Use a single mailbox for warm reset for FVP and Juno

Since there is a unique warm reset entry point, the FVP and Juno
port can use a single mailbox instead of maintaining one per core.
The mailbox gets programmed only once when plat_setup_psci_ops()
is invoked during PSCI initialization. This means mailbox is not
zeroed out during wakeup.

Change-Id: Ieba032a90b43650f970f197340ebb0ce5548d432
diff --git a/include/plat/arm/css/common/css_def.h b/include/plat/arm/css/common/css_def.h
index 268438f..e3dd2b0 100644
--- a/include/plat/arm/css/common/css_def.h
+++ b/include/plat/arm/css/common/css_def.h
@@ -39,8 +39,7 @@
  *************************************************************************/
 #define MHU_PAYLOAD_CACHED		0
 
-#define TRUSTED_MAILBOXES_BASE		ARM_TRUSTED_SRAM_BASE
-#define TRUSTED_MAILBOX_SHIFT		4
+#define TRUSTED_MAILBOX_BASE		ARM_TRUSTED_SRAM_BASE
 
 #define NSROM_BASE			0x1f000000
 #define NSROM_SIZE			0x00001000