AMDGPU: Reduce AddedComplexity on canonicalize pattern (#119796)

Pick the minimum complexity required for tests to pass instead of
a giant debug value of 1000.

Author: arsenm

llvm/lib/Target/AMDGPU/SIInstructions.td

@@ -3055,7 +3055,7 @@ def : GCNPat<
    (V_BFREV_B32_e64 (i32 (EXTRACT_SUBREG VReg_64:$a, sub0))), sub1)>;
 
 // If fcanonicalize's operand is implicitly canonicalized, we only need a copy.
-let AddedComplexity = 1000 in {
+let AddedComplexity = 8 in {
 foreach vt = [f16, v2f16, f32, v2f32, f64] in {
   def : GCNPat<
     (fcanonicalize (vt is_canonicalized:$src)),