JitArm64: Improve srawx special case carry calculation

At a first glance it may look like a part of the code I added to
srawx in efeda3b has a bug when a == s. The code actually happens
to work correctly, but in the interest of making the code easier
to reason about, I'd like to change the way it's implemented. This
change should improve the pipelining a little in the a == s case too.

Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp

@@ -1401,13 +1401,14 @@ void JitArm64::srawx(UGeckoInstruction inst)
     {
       gpr.BindToRegister(a, a == s);
 
-      ASR(gpr.R(a), gpr.R(s), 31);
-
       if (js.op->wantsCA)
       {
+        // Set the carry flag to the sign bit of s
         CMN(gpr.R(s), gpr.R(s));
         ComputeCarry();
       }
+
+      ASR(gpr.R(a), gpr.R(s), 31);
     }
     else if (amount == 0)
     {