tipc: fix a bit overflow in tipc_crypto_key_rcv()

[ Upstream commit 143de8d9 ]

msg_data_sz return a 32bit value, but size is 16bit. This may lead to a
bit overflow.

Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>