ib_pack.h: Add opcode definition for send with invalidate

The opcode for "SEND Last with Invalidate" and "SEND Only with
Invalidate" have been defined for RC in IBA Specification Vol 1
since Release 1.2. Add the definition to the header file in
preparation of supporting these opcodes in rdmavt based drivers.

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Jianxin Xiong <jianxin.xiong@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>