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/mem/cache/BaseCache.py

@@ -37,7 +37,7 @@ class BaseCache(MemObject):
     assoc = Param.Int("associativity")
     block_size = Param.Int("block size in bytes")
     latency = Param.Latency("Latency")
-    hash_delay = Param.Int(1, "time in cycles of hash access")
+    hash_delay = Param.Cycles(1, "time in cycles of hash access")
     max_miss_count = Param.Counter(0,
         "number of misses to handle before calling exit")
     mshrs = Param.Int("number of MSHRs (max outstanding requests)")