IB/cm: Remove unused and erroneous msg sequence encoding

In cm_form_tid(), a two bit message sequence number is OR'ed into bit
31-30 of the lower TID value.

After commit f06d2653 ("IB/cm: Randomize starting comm ID"), the
local_id is XOR'ed with a 32-bit random value. Hence, bit 31-30 in the
lower TID now has an arbitrarily value and it makes no sense to OR in
the message sequence number.

Adding to that, the evolution in use of IDR routines in cm_alloc_id()
has always had the possibility of returning a value with bit 30 set.

In addition, said bits are never checked.

Hence, remove the encoding and the corresponding enum.

Signed-off-by: Håkon Bugge <haakon.bugge@oracle.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>