sim: Remove the unused SimObject::regFormulas method

Simulation objects normally register derived statistics, presumably
what regFormulas originally was meant for, in regStats(). This patch
removes regRegformulas since there is no need to have a separate
method call to register formulas.

src/python/m5/simulate.py

@@ -110,7 +110,6 @@ def instantiate(ckpt_dir=None):
 
     # Do a third pass to initialize statistics
     for obj in root.descendants(): obj.regStats()
-    for obj in root.descendants(): obj.regFormulas()
 
     # We're done registering statistics.  Enable the stats package now.
     stats.enable()