Use correct type when reading SCR register

The Secure Configuration Register is 64-bits in AArch64 and 32-bits in
AArch32. Use u_register_t instead of unsigned int to reflect this.

Change-Id: I51b69467baba36bf0cfaec2595dc8837b1566934
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>
diff --git a/include/lib/el3_runtime/context_mgmt.h b/include/lib/el3_runtime/context_mgmt.h
index 7c996d1..17955e3 100644
--- a/include/lib/el3_runtime/context_mgmt.h
+++ b/include/lib/el3_runtime/context_mgmt.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -45,7 +45,7 @@
 			  uint32_t bit_pos,
 			  uint32_t value);
 void cm_set_next_eret_context(uint32_t security_state);
-uint32_t cm_get_scr_el3(uint32_t security_state);
+u_register_t cm_get_scr_el3(uint32_t security_state);
 
 /* Inline definitions */