fix(el3_runtime): correct CASSERT for pauth

clang build breaks when both ENABLE_PAUTH (BRANCH_PROTECTOR=1)
and CRASH_REPORTING (DEBUG=1) options are enabled:

include/lib/el3_runtime/cpu_data.h:135:2: error: redefinition of typedef
'assert_cpu_data_crash_stack_offset_mismatch' is a C11 feature [-Werror,
-Wtypedef-redefinition]
        assert_cpu_data_crash_stack_offset_mismatch);
        ^
include/lib/el3_runtime/cpu_data.h:128:2: note: previous definition is here
        assert_cpu_data_crash_stack_offset_mismatch);
        ^
1 error generated.
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: I22c8c45a94a64620007979d55412dbb57b11b813

include/lib/el3_runtime/cpu_data.h

 /*
- * Copyright (c) 2014-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2014-2021, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -125,7 +125,7 @@ extern cpu_data_t percpu_data[PLATFORM_CORE_COUNT];
 #if ENABLE_PAUTH
 CASSERT(CPU_DATA_APIAKEY_OFFSET == __builtin_offsetof
 	(cpu_data_t, apiakey),
-	assert_cpu_data_crash_stack_offset_mismatch);
+	assert_cpu_data_pauth_stack_offset_mismatch);
 #endif
 
 #if CRASH_REPORTING