fix(bl31): add const qualifier

This corrects the MISRA violation C2012-8.13:
A pointer should point to a const-qualified type whenever possible.
Added const qualifier to pointer in the function arguments.

Change-Id: Ia323a2b2946d61a639696e2559f88e376beda861
Signed-off-by: Nithin G <nithing@amd.com>
Signed-off-by: Maheedhar Bollapalli <maheedharsai.bollapalli@amd.com>
diff --git a/bl31/bl31_main.c b/bl31/bl31_main.c
index db0ea6c..0cd0c79 100644
--- a/bl31/bl31_main.c
+++ b/bl31/bl31_main.c
@@ -255,7 +255,7 @@
  ******************************************************************************/
 void __init bl31_prepare_next_image_entry(void)
 {
-	entry_point_info_t *next_image_info;
+	const entry_point_info_t *next_image_info;
 	uint32_t image_type;
 
 #if CTX_INCLUDE_AARCH32_REGS