Replace S-EL3 references by EL3

The "Secure" prefix (S-ELx) is valid only for S-EL0 and S-EL1 but is
meaningless for EL3, since EL3 is always secure. Hence, the "S" prefix
has been removed from wherever it was used as "S-EL3".

Change-Id: Icdeac9506d763f9f83d7297c7113aec7b85e9dbe
Signed-off-by: John Tsichritzis <john.tsichritzis@arm.com>
diff --git a/plat/rpi3/rpi3_bl31_setup.c b/plat/rpi3/rpi3_bl31_setup.c
index 306f26b..0ae783e 100644
--- a/plat/rpi3/rpi3_bl31_setup.c
+++ b/plat/rpi3/rpi3_bl31_setup.c
@@ -47,7 +47,7 @@
 
 /*******************************************************************************
  * Perform any BL31 early platform setup. Here is an opportunity to copy
- * parameters passed by the calling EL (S-EL1 in BL2 & S-EL3 in BL1) before
+ * parameters passed by the calling EL (S-EL1 in BL2 & EL3 in BL1) before
  * they are lost (potentially). This needs to be done before the MMU is
  * initialized so that the memory layout can be used while creating page
  * tables. BL2 has flushed this information to memory, so we are guaranteed