refactor(cpufeat): separate the EL2 and EL3 enablement code

Combining the EL2 and EL3 enablement code necessitates that it must be
called at el3_exit, which is the only place with enough context to make
the decision of what needs to be set.
Decouple them to allow them to be called from elsewhere.

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: I147764c42771e7d4100699ec8fae98dac0a505c0
diff --git a/include/lib/extensions/sys_reg_trace.h b/include/lib/extensions/sys_reg_trace.h
index 5915c55..d9f7f1b 100644
--- a/include/lib/extensions/sys_reg_trace.h
+++ b/include/lib/extensions/sys_reg_trace.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, Arm Limited. All rights reserved.
+ * Copyright (c) 2021-2023, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -10,10 +10,12 @@
 #include <context.h>
 
 #if ENABLE_SYS_REG_TRACE_FOR_NS
+
 #if __aarch64__
 void sys_reg_trace_enable(cpu_context_t *context);
+void sys_reg_trace_init_el2_unused(void);
 #else
-void sys_reg_trace_enable(void);
+void sys_reg_trace_init_el3(void);
 #endif /* __aarch64__ */
 
 #else /* !ENABLE_SYS_REG_TRACE_FOR_NS */
@@ -22,11 +24,18 @@
 static inline void sys_reg_trace_enable(cpu_context_t *context)
 {
 }
+static inline void sys_reg_trace_disable(cpu_context_t *context)
+{
+}
+static inline void sys_reg_trace_init_el2_unused(void)
+{
+}
 #else
-static inline void sys_reg_trace_enable(void)
+static inline void sys_reg_trace_init_el3(void)
 {
 }
 #endif /* __aarch64__ */
+
 #endif /* ENABLE_SYS_REG_TRACE_FOR_NS */
 
 #endif /* SYS_REG_TRACE_H */