feat(rmmd): add support for RMM Boot interface

This patch adds the infrastructure needed to pass boot arguments from
EL3 to RMM and allocates a shared buffer between both worlds that can
be used, among others, to pass a boot manifest to RMM. The buffer is
composed a single memory page be used by a later EL3 <-> RMM interface
by all CPUs.

The RMM boot manifest is not implemented by this patch.

In addition to that, this patch also enables support for RMM when
RESET_TO_BL31 is enabled.

Signed-off-by: Javier Almansa Sobrino <javier.almansasobrino@arm.com>
Change-Id: I855cd4758ee3843eadd9fb482d70a6d18954d82a
diff --git a/include/plat/arm/common/plat_arm.h b/include/plat/arm/common/plat_arm.h
index 9618700..d060332 100644
--- a/include/plat/arm/common/plat_arm.h
+++ b/include/plat/arm/common/plat_arm.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2021, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2022, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -57,7 +57,8 @@
 	{ARM_EL3_TZC_DRAM1_BASE, ARM_L1_GPT_END, TZC_REGION_S_RDWR, 0},	    \
 	{ARM_NS_DRAM1_BASE, ARM_NS_DRAM1_END, ARM_TZC_NS_DRAM_S_ACCESS,	    \
 		PLAT_ARM_TZC_NS_DEV_ACCESS},				    \
-	{ARM_REALM_BASE, ARM_REALM_END, ARM_TZC_NS_DRAM_S_ACCESS,	    \
+	/* Realm and Shared area share the same PAS */		    \
+	{ARM_REALM_BASE, ARM_EL3_RMM_SHARED_END, ARM_TZC_NS_DRAM_S_ACCESS,  \
 		PLAT_ARM_TZC_NS_DEV_ACCESS},				    \
 	{ARM_DRAM2_BASE, ARM_DRAM2_END, ARM_TZC_NS_DRAM_S_ACCESS,	    \
 		PLAT_ARM_TZC_NS_DEV_ACCESS}