Revert "migen/actorlib/fifo: add FIFO wrapper function"

This reverts commit d0a19c4be8.

migen/actorlib/fifo.py

@@ -55,15 +55,3 @@ class SyncFIFO(_FIFOActor):
 class AsyncFIFO(_FIFOActor):
     def __init__(self, layout, depth):
         _FIFOActor.__init__(self, fifo.AsyncFIFO, layout, depth)
-
-
-def FIFO(layout, depth, buffered=False,
-          sink_cd="sys", source_cd="sys"):
-    if sink_cd != source_cd:
-        if buffered:
-            ValueError("AsyncFIFO does not support buffered mode")
-        fifo = AsyncFIFO(layout, depth)
-        return ClockDomainsRenamer({"write": sink_cd, "read": source_cd})(fifo)
-    else:
-        fifo = SyncFIFO(layout, depth, buffered)
-        return ClockDomainsRenamer(sink_cd)(fifo)