Implement support for SMCCC v1.1

SMCCC v1.1 comes with a relaxed calling convention for AArch64
callers.  The caller only needs to save x0-x3 before doing an SMC
call.

This patch adds support for SMCCC_VERSION and SMCCC_ARCH_FEATURES.

Refer to "Firmware Interfaces for mitigating CVE_2017_5715 System
Software on Arm Systems"[0] for more information.

[0] https://developer.arm.com/-/media/developer/pdf/ARM%20DEN%200070A%20Firmware%20interfaces%20for%20mitigating%20CVE-2017-5715_V1.0.pdf

Change-Id: If5b1c55c17d6c5c7cb9c2c3ed355d3a91cdad0a9
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
diff --git a/include/services/arm_arch_svc.h b/include/services/arm_arch_svc.h
new file mode 100644
index 0000000..2961601
--- /dev/null
+++ b/include/services/arm_arch_svc.h
@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef __ARM_ARCH_SVC_H__
+#define __ARM_ARCH_SVC_H__
+
+#define SMCCC_VERSION			U(0x80000000)
+#define SMCCC_ARCH_FEATURES		U(0x80000001)
+#define SMCCC_ARCH_WORKAROUND_1		U(0x80008000)
+
+#endif /* __ARM_ARCH_SVC_H__ */