Bluetooth: Fix l2cap_sock_setsockopt() with optname BT_RCVMTU

When we retrieve imtu value from userspace we should use 16 bit pointer
cast instead of 32 as it's defined that way in headers. Fixes setsockopt
calls on big-endian platforms.

Signed-off-by: Amadeusz Sławiński <amadeusz.slawinski@tieto.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Cc: stable@vger.kernel.org
diff --git a/net/bluetooth/l2cap_sock.c b/net/bluetooth/l2cap_sock.c
index 388ee8b..1842141 100644
--- a/net/bluetooth/l2cap_sock.c
+++ b/net/bluetooth/l2cap_sock.c
@@ -927,7 +927,7 @@
 			break;
 		}
 
-		if (get_user(opt, (u32 __user *) optval)) {
+		if (get_user(opt, (u16 __user *) optval)) {
 			err = -EFAULT;
 			break;
 		}