[RISCV] Add missing hunk to #67889 to fix test failures

Without this, various CodeGen tests fail because a
RISCV::FCVT_D_W[_IN32X] machine node is created without the rounding
mode operand.

The relevant PR was committed as bf94ba39b65d1212ea84d5783b393280e1ce7478

GitOrigin-RevId: 0b0ed8f76a264c3677b8254d8d334de43600568f
1 file changed