sysfs: fix minor compile warning

Seen in Debian QA on mipsel.

util-sysfs.c: In function ‘SysFsWriteValue’:
util-sysfs.c:50:45: warning: format ‘%ld’ expects argument of type ‘long int’, but argument 4 has type ‘int64_t’ {aka ‘long long int’} [-Wformat=]
   50 |     snprintf(sentence, sizeof(sentence), "%ld", value);
      |                                           ~~^   ~~~~~
      |                                             |   |
      |                                             |   int64_t {aka long long int}
      |                                             long int
      |                                           %lld

src/util-sysfs.c

@@ -47,7 +47,7 @@ TmEcode SysFsWriteValue(const char *path, int64_t value)
         SCReturnInt(TM_ECODE_FAILED);
     }
 
-    snprintf(sentence, sizeof(sentence), "%ld", value);
+    snprintf(sentence, sizeof(sentence), "%" PRIu64, value);
     ssize_t len = strlen(sentence);
 
     if (write(fd, sentence, len) != len) {