When -triple is windows, SelectionDAGLegalize process Legalizing br_jt,
would generate ISD::JUMP_TABLE_DEBUG_INFO.
Then Mips process emitInstruction, would think JUMP_TABLE_DEBUG_INFO is
a pseudo instruction and generate an error `Pseudo opcode found in
emitInstruction()`.
This instruction `TargetOpcode::JUMP_TABLE_DEBUG_INFO` is only used to
note jump table debug info, so we can ignore it when Mips emit
instruction.
Fix#134916.
bbe5ceb22f