feat(debugv8p9): test if EL3 has properly enabled FEAT_Debugv8p9

When FEAT_Debugv8p9 is not enabled, access to MDSELR_EL1
traps to EL3. Access to FEAT_DEBUGV8P9 control registers
must be explicitly enabled in EL3,

This testcase uses this behavior to test if
FEAT_Debugv8p9 is enabled or not.

Change-Id: I2f9a0158e9f38eaffac2e27c40d44d3c520d508d
Signed-off-by: Arvind Ram Prakash <arvind.ramprakash@arm.com>
diff --git a/include/lib/aarch64/arch_helpers.h b/include/lib/aarch64/arch_helpers.h
index 4b9c33e..a91625c 100644
--- a/include/lib/aarch64/arch_helpers.h
+++ b/include/lib/aarch64/arch_helpers.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2023, Arm Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2024, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -611,6 +611,8 @@
 DEFINE_RENAME_SYSREG_RW_FUNCS(trcclaimclr, TRCCLAIMCLR)
 DEFINE_RENAME_SYSREG_READ_FUNC(trcdevarch, TRCDEVARCH)
 
+DEFINE_RENAME_SYSREG_READ_FUNC(mdselr_el1, MDSELR_EL1)
+
 /* FEAT_HCX HCRX_EL2 */
 DEFINE_RENAME_SYSREG_RW_FUNCS(hcrx_el2, HCRX_EL2)