audit_log_untrustedstring() warning fix

kernel/audit.c: In function `audit_log_untrustedstring':
kernel/audit.c:736: warning: comparison is always false due to limited range of data type
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>

kernel/audit.c

@@ -730,7 +730,7 @@ void audit_log_hex(struct audit_buffer *ab, const unsigned char *buf, size_t len
 
 void audit_log_untrustedstring(struct audit_buffer *ab, const char *string)
 {
-	const char *p = string;
+	const unsigned char *p = string;
 
 	while (*p) {
 		if (*p == '"' || *p == ' ' || *p < 0x20 || *p > 0x7f) {