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: Andrew Morton <akpm@osdl.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/kernel/audit.c b/kernel/audit.c
index dca7b99..e7bff80 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -730,7 +730,7 @@
 
 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) {