[DAG] visitVSELECT - move OpLHS == LHS into inner if() in USUBSAT matching. NFCI.

This will be necessary for the update of D25987 where we'll need to match OpLHS against other ops.

GitOrigin-RevId: e47f21da6153159809f84aa3d6b7d78113e7842f
1 file changed