ahb: weaken RegisterRouter assertion

As written I think it could potentially fail, but what I actually care
about is something weaker that should be true. Assert: nothing lost.

src/main/scala/uncore/ahb/RegisterRouter.scala

@@ -52,7 +52,7 @@ class AHBRegisterNode(address: AddressSet, concurrency: Int = 0, beatBytes: Int
 
     val request = ahb.htrans === AHBParameters.TRANS_NONSEQ || ahb.htrans === AHBParameters.TRANS_SEQ
     when (ahb.hready && ahb.hsel && request) {
-      assert (!d_phase || in.ready)
+      assert (!in.valid || in.ready)
       d_phase := Bool(true)
       d_taken := Bool(false)
       d_read  := !ahb.hwrite