aco/wave32: Use lane mask regclass for exec/vcc.

Currently all usages of exec and vcc are hardcoded to use s2 regclass.
This commit makes it possible to use s1 in wave32 mode and
s2 in wave64 mode.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>

src/amd/compiler/aco_reduce_assign.cpp

@@ -172,7 +172,7 @@ void setup_reduce_temp(Program* program)
             clobber_vcc = true;
 
          if (clobber_vcc)
-            instr->definitions[4] = Definition(vcc, s2);
+            instr->definitions[4] = Definition(vcc, bld.lm);
       }
    }
 }