staging: panel: fix interruptible_sleep_on race

interruptible_sleep_on is racy and going away. This replaces the one
caller in the panel driver with the appropriate wait_event_interruptible
variant.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: devel@driverdev.osuosl.org
Cc: Willy Tarreau <willy@meta-x.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/panel/panel.c

@@ -1590,8 +1590,8 @@ static ssize_t keypad_read(struct file *file,
 		if (file->f_flags & O_NONBLOCK)
 			return -EAGAIN;
 
-		interruptible_sleep_on(&keypad_read_wait);
-		if (signal_pending(current))
+		if (wait_event_interruptible(keypad_read_wait,
+					     keypad_buflen != 0))
 			return -EINTR;
 	}