Param: Transition to Cycles for relevant parameters

This patch is a first step to using Cycles as a parameter type. The
main affected modules are the CPUs and the Ruby caches. There are
definitely plenty more places that are affected, but this patch serves
as a starting point to making the transition.

An important part of this patch is to actually enable parameters to be
specified as Param.Cycles which involves some changes to params.py.

src/cpu/FuncUnit.py

@@ -53,9 +53,9 @@ class OpClass(Enum):
 
 class OpDesc(SimObject):
     type = 'OpDesc'
-    issueLat = Param.Int(1, "cycles until another can be issued")
+    issueLat = Param.Cycles(1, "cycles until another can be issued")
     opClass = Param.OpClass("type of operation")
-    opLat = Param.Int(1, "cycles until result is available")
+    opLat = Param.Cycles(1, "cycles until result is available")
 
 class FUDesc(SimObject):
     type = 'FUDesc'