tty: hvc_console: silence unintialized variable warning

If ->get_char() returns a negative error code and that can mean that
"ch" is uninitialized.  The callers of this function expect NO_POLL_CHAR
on error so let's return that.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/hvc/hvc_console.c

@@ -814,7 +814,7 @@ static int hvc_poll_get_char(struct tty_driver *driver, int line)
 
 	n = hp->ops->get_chars(hp->vtermno, &ch, 1);
 
-	if (n == 0)
+	if (n <= 0)
 		return NO_POLL_CHAR;
 
 	return ch;