[RISCV] Remove traces of Glue from RISCVISD::SELECT_CC

We were creating RISCVISD::SELECT_CC nodes with Glue output that was never being used, and the tablegen SDNode had the SDNPInGlue flag instead of the SDNPOutGlue flag.

Since we don't seem to need the Glue just get rid of it from both places.

Differential Revision: https://reviews.llvm.org/D91199