arch-gcn3,arch-vega: Don't write exec in v_cmp_f_i32

Per the GCN3 and VEGA ISAs, v_cmpx_* writes exec, while v_cmp_* doesn't.

This removes the erroneous exec write in the VOP3 implementation of
v_cmp_f_i32.

Change-Id: I048e35917163c45b879f38d31a88f3f3d56c0baf
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52445
Maintainer: Matt Sinclair <mattdsinclair@gmail.com>
Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com>
Reviewed-by: Matthew Poremba <matthew.poremba@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/amdgpu/gcn3/insts/instructions.cc

@@ -20601,7 +20601,6 @@ namespace Gcn3ISA
             }
         }
 
-        wf->execMask() = sdst.rawData();
         sdst.write();
     }
 

src/arch/amdgpu/vega/insts/instructions.cc

@@ -22454,7 +22454,6 @@ namespace VegaISA
             }
         }
 
-        wf->execMask() = sdst.rawData();
         sdst.write();
     } // execute
     // --- Inst_VOP3__V_CMP_LT_I32 class methods ---