ibcore: 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 Linux commit f06d26537559 ("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.

Linux commit:
87a37ce9e400e40daee537ff95343e3c94743c6d

Reviewed by: kib
Sponsored by: Mellanox Technologies // NVIDIA Networking

(cherry picked from commit 315627b7191dd4fe30a9293609feaf7eeb62e478)