notes: Initialise variable to appease gcc

gcc version 3.4.4 thinks that the 'cmp' variable could be used
while uninitialised and complains thus:

    notes.c: In function `write_each_non_note_until':
    notes.c:719: warning: 'cmp' might be used uninitialized in \
        this function

Note that gcc versions 4.1.2 and 4.4.0 do not issue this warning.
Signed-off-by: NRamsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

notes.c

@@ -716,7 +716,7 @@ static int write_each_non_note_until(const char *note_path,
 		struct write_each_note_data *d)
 {
 	struct non_note *n = d->next_non_note;
-	int cmp, ret;
+	int cmp = 0, ret;
 	while (n && (!note_path || (cmp = strcmp(n->path, note_path)) <= 0)) {
 		if (note_path && cmp == 0)
 			; /* do nothing, prefer note to non-note */