Fix MISRA defects in log helpers

No functional changes.

Change-Id: I850f08718abb69d5d58856b0e3de036266d8c2f4
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/plat/common/plat_log_common.c b/plat/common/plat_log_common.c
index 30dcb12..49e1c15 100644
--- a/plat/common/plat_log_common.c
+++ b/plat/common/plat_log_common.c
@@ -1,25 +1,28 @@
 /*
- * Copyright (c) 2017, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2017-2018, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
-#include <assert.h>
 #include <debug.h>
-#include <platform.h>
 
 /* Allow platforms to override the log prefix string */
 #pragma weak plat_log_get_prefix
 
-static const char *prefix_str[] = {
+static const char *plat_prefix_str[] = {
 	"ERROR:   ", "NOTICE:  ", "WARNING: ", "INFO:    ", "VERBOSE: "};
 
 const char *plat_log_get_prefix(unsigned int log_level)
 {
-	if (log_level < LOG_LEVEL_ERROR)
-		log_level = LOG_LEVEL_ERROR;
-	else if (log_level > LOG_LEVEL_VERBOSE)
-		log_level = LOG_LEVEL_VERBOSE;
+	unsigned int level;
 
-	return prefix_str[(log_level/10) - 1];
+	if (log_level < LOG_LEVEL_ERROR) {
+		level = LOG_LEVEL_ERROR;
+	} else if (log_level > LOG_LEVEL_VERBOSE) {
+		level = LOG_LEVEL_VERBOSE;
+	} else {
+		level = log_level;
+	}
+
+	return plat_prefix_str[(level / 10U) - 1U];
 }