rsocket: Expand definition of target SGE

rsocket: Expand definition of target SGE

During connection establishment, rsocket exchanges a
target SGE.  The target SGE contains the address, rkey,
and length of the target SGL.  The target SGL is the
location where rsocket publishes data buffers at the
remote peer.

The length contained in the target SGE is the number of
entries in the target SGL, which is currently set to 2.
Divide the length field into 3 separate values.

bits 31:16 - reserved
bits 15:8  - use for direct data placement algorithm
bits 7:0   - use for target SGL size

Bits 15 and 7 are used as scaling factors.  If set, then
the size specified in the corresponding lower bits is
multiplied by 128.

Backwards compatibility is maintained, since we never use
a value greater than 2 anyway.

Signed-off-by: Sean Hefty <sean.hefty@intel.com>