Fixes the OP_vpgatherqd and OP_vpgatherqq disassembly string names which were incorrect.
I would like to add a test to ir_all_opc.h to find string-vs-opcode mismatches but it is not simple to do so I bailed on it here.
Fixes the encoding chains for OP_vpgather* which should all be singletons.
Issue: #2985 (closed)