fix: rename Matterhorn, Matterhorn ELP, and Klein CPUs

This patch renames the Matterhorn, Matterhorn ELP, and Klein CPUs to
Cortex A710, Cortex X2, and Cortex A510 respectively.

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: I056d3114210db71c2840a24562b51caf2546e195
diff --git a/include/lib/cpus/aarch64/cortex_a710.h b/include/lib/cpus/aarch64/cortex_a710.h
new file mode 100644
index 0000000..44c540c
--- /dev/null
+++ b/include/lib/cpus/aarch64/cortex_a710.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2021, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef CORTEX_A710_H
+#define CORTEX_A710_H
+
+#define CORTEX_A710_MIDR					U(0x410FD470)
+
+/*******************************************************************************
+ * CPU Extended Control register specific definitions
+ ******************************************************************************/
+#define CORTEX_A710_CPUECTLR_EL1				S3_0_C15_C1_4
+
+/*******************************************************************************
+ * CPU Power Control register specific definitions
+ ******************************************************************************/
+#define CORTEX_A710_CPUPWRCTLR_EL1				S3_0_C15_C2_7
+#define CORTEX_A710_CPUPWRCTLR_EL1_CORE_PWRDN_BIT		U(1)
+
+#endif /* CORTEX_A710_H */