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/plat/mediatek/mt6795/bl31_plat_setup.c b/plat/mediatek/mt6795/bl31_plat_setup.c
index 96a0bd8..8df7dad 100644
--- a/plat/mediatek/mt6795/bl31_plat_setup.c
+++ b/plat/mediatek/mt6795/bl31_plat_setup.c
@@ -339,7 +339,7 @@
 	next_image_info = &bl33_image_ep_info;
 
 	/* Figure out what mode we enter the non-secure world in */
-	if (EL_IMPLEMENTED(2)) {
+	if (el_implemented(2) != EL_IMPL_NONE) {
 		INFO("Kernel_EL2\n");
 		mode = MODE_EL2;
 	} else{