RegField: remove RegField.bytes; it was dangerous

The implementation unconditionally drove the register.
This made it incompatible with drivers from the device itself.
Besides, writing only parts of a register at a time is ultra-shady.

src/main/scala/uncore/tilelink2/RegField.scala

@@ -106,21 +106,6 @@ object RegField
       Bool(true)
     }))
 
-  // Split a large register into a sequence of byte fields
-  // The bytes can be individually written, as they are one byte per field
-  def bytes(x: UInt): Seq[RegField] = {
-    require (x.getWidth % 8 == 0)
-    val bytes = Seq.tabulate(x.getWidth/8) { i => x(8*(i+1)-1, 8*i) }
-    val wires = bytes.map { b => Wire(init = b) }
-    x := Cat(wires.reverse)
-    Seq.tabulate(x.getWidth/8) { i =>
-      RegField(8, bytes(i), RegWriteFn { (valid, data) =>
-        when (valid) { wires(i) := data }
-        Bool(true)
-      })
-    }
-  }
-
   // Divide a long sequence of RegFields into a maximum sized registers
   // Your input RegFields may not cross a beatBytes boundary!
   def split(fields: Seq[RegField], base: Int, beatBytes: Int = 4): Seq[RegField.Map] = {