thunderbolt: Fix a couple right shifting to zero bugs

The problematic code looks like this:

	res_seq = res_hdr->xd_hdr.length_sn & TB_XDOMAIN_SN_MASK;
	res_seq >>= TB_XDOMAIN_SN_SHIFT;

TB_XDOMAIN_SN_SHIFT is 27, and right shifting a u8 27 bits is always
going to result in zero.  The fix is to declare these variables as u32.

Fixes: d1ff7024 ("thunderbolt: Add support for XDomain discovery protocol")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>