arch: Make the generic micropc enabled PCState set nupc to 1.

The default constructor of the micropc enabled generic PCState class
set the next micropc to 0, when the non-default constructor and at
least the x86 initCPU utility function set it to 1. This makes more
sense since either the micropc doesn't matter as a concept if the
instruction isn't microcoded, or, unless redirected by a micropc
branch, you're going to want to execute the next microop and not just
repeat the first one.

Change-Id: I418ea986a071453563c4c8aad4fc4eb4f7beb641
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24184
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/generic/types.hh

@@ -222,7 +222,7 @@ class UPCState : public SimplePCState<MachInst>
         nupc(1);
     }
 
-    UPCState() : _upc(0), _nupc(0) {}
+    UPCState() : _upc(0), _nupc(1) {}
     UPCState(Addr val) : _upc(0), _nupc(0) { set(val); }
 
     bool