Improve display_boot_progress() function

- Remove out-dated information about the use of printf() in the
   function comment.

 - Make the argument const, as the function doesn't need to modify it.

 - Rename the function into bl1_print_bl31_ep_info() to make its
   purpose clearer.

Change-Id: I2a9d215a37f0ec11aefce0c5c9e050473b7a6b25

bl1/aarch64/bl1_exceptions.S

@@ -195,7 +195,7 @@ func smc_handler64
 	b.ne	unexpected_sync_exception
 
 	mov	x0, x20
-	bl	display_boot_progress
+	bl	bl1_print_bl31_ep_info
 
 	ldp	x0, x1, [x20, #ENTRY_POINT_INFO_PC_OFFSET]
 	msr	elr_el3, x0

bl1/bl1_main.c

@@ -199,10 +199,11 @@ void bl1_main(void)
 }
 
 /*******************************************************************************
- * Temporary function to print the fact that BL2 has done its job and BL31 is
- * about to be loaded. This is needed as long as printfs cannot be used
+ * Function called just before handing over to BL31 to inform the user about
+ * the boot progress. In debug mode, also print details about the BL31 image's
+ * execution context.
  ******************************************************************************/
-void display_boot_progress(entry_point_info_t *bl31_ep_info)
+void bl1_print_bl31_ep_info(const entry_point_info_t *bl31_ep_info)
 {
 	NOTICE("BL1: Booting BL3-1\n");
 	print_entry_point_info(bl31_ep_info);