Introduce IS_IN_ELX() macros

The goal of these macros is to improve code readability by providing
a concise way to check whether we are running in the expected
exception level.

Change-Id: If9aebadfb6299a5196e9a582b442f0971d9909b1
diff --git a/common/bl_common.c b/common/bl_common.c
index 5361c38..86b0cc5 100644
--- a/common/bl_common.c
+++ b/common/bl_common.c
@@ -106,9 +106,7 @@
  */
 void __dead2 change_el(el_change_info_t *info)
 {
-	unsigned long current_el = read_current_el();
-
-	if (GET_EL(current_el) == MODE_EL3) {
+	if (IS_IN_EL3()) {
 		/*
 		 * We can go anywhere from EL3. So find where.
 		 * TODO: Lots to do if we are going non-secure.
@@ -551,7 +549,6 @@
 		       void *second_arg)
 {
 	el_change_info_t run_image_info;
-	unsigned long current_el = read_current_el();
 
 	/* Tell next EL what we want done */
 	run_image_info.args.arg0 = RUN_IMAGE;
@@ -565,7 +562,7 @@
 	 * to jump to a higher EL and issue an SMC. Contents of argY
 	 * will go into the general purpose register xY e.g. arg0->x0
 	 */
-	if (GET_EL(current_el) == MODE_EL3) {
+	if (IS_IN_EL3()) {
 		run_image_info.args.arg1 = (unsigned long) first_arg;
 		run_image_info.args.arg2 = (unsigned long) second_arg;
 	} else {