context_mgmt: Fix MISRA defects

The macro EL_IMPLEMENTED() has been deprecated in favour of the new
function el_implemented().

Change-Id: Ic9b1b81480b5e019b50a050e8c1a199991bf0ca9
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/include/lib/aarch32/arch_helpers.h b/include/lib/aarch32/arch_helpers.h
index 5d9c1c1..03f0e86 100644
--- a/include/lib/aarch32/arch_helpers.h
+++ b/include/lib/aarch32/arch_helpers.h
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#ifndef __ARCH_HELPERS_H__
-#define __ARCH_HELPERS_H__
+#ifndef ARCH_HELPERS_H
+#define ARCH_HELPERS_H
 
 #include <arch.h>	/* for additional register definitions */
 #include <cdefs.h>
@@ -381,4 +381,4 @@
 #define write_icc_sgi0r_el1(_v) \
 		write64_icc_sgi0r_el1(_v)
 
-#endif /* __ARCH_HELPERS_H__ */
+#endif /* ARCH_HELPERS_H */