[MSP430] Remove unused MVT::Glue output from MSP430ISD::SELECT_CC nodes.

Follow up from a similar patch on RISCV 637f19c3

Nothing reads this Glue value that I could see. The SDNode def in
the td file does not have the SDNPOutGlue flag so I don't think
this glue would get properly propagated to MachineSDNodes if it
was used.