util/logopenfile: fix compile warnings

util-logopenfile.c:837:11: error: initializing 'char *' with an expression of type 'const char *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
  837 |     char *dot = strrchr(base, '.');
      |           ^     ~~~~~~~~~~~~~~~~~~
util-logopenfile.c:848:13: error: assigning to 'char *' from 'const char *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
  848 |         dot = strrchr(original_name, '.');
      |             ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
2 errors generated.

src/util-logopenfile.c

@@ -834,7 +834,7 @@ static bool LogFileThreadedName(
     }
 
     /* Check if basename has an extension */
-    char *dot = strrchr(base, '.');
+    const char *dot = strrchr(base, '.');
     if (dot) {
         char *tname = SCStrdup(original_name);
         if (!tname) {