Remove unused signal from TLB interface

src/main/scala/rocket/TLB.scala

@@ -27,7 +27,6 @@ class TLBReq(lgMaxSize: Int)(implicit p: Parameters) extends CoreBundle()(p) {
   val vaddr = UInt(width = vaddrBitsExtended)
   val passthrough = Bool()
   val instruction = Bool()
-  val store = Bool()
   val sfence = Valid(new SFenceReq)
   val size = UInt(width = log2Ceil(lgMaxSize + 1))
   val cmd  = Bits(width = M_SZ)