Revert "Intentionally broke wally by setting datapath Rs1D to use bits 18:14 instead of 19:15 to test regression"

This reverts commit 4908f77cf9.

unbroke wally

pipelined/src/ieu/datapath.sv

@@ -88,7 +88,7 @@ module datapath (
   logic [`XLEN-1:0] IFResultW;
   
   // Decode stage
-  assign Rs1D      = InstrD[18:14]; // Broke this, it should be 19 to 15.
+  assign Rs1D      = InstrD[19:15];
   assign Rs2D      = InstrD[24:20];
   assign RdD       = InstrD[11:7];
   regfile regf(clk, reset, RegWriteW, Rs1D, Rs2D, RdW, ResultW, R1D, R2D);