Add Frequency and Latency as new parameter types and use them

Add Frequency and Latency as new parameter types and use them
where we can

python/m5/config.py:
    Add two new parameter types: Frequency and Latency.  These will soon
    be an integral part of the tick is picosecond thing.  If the value
    can be converted directly to an integer without any special tricks,
    we assume that the number is the exact value desired.  Otherwise,
    we convert the number assuming that it is in Hz or s.
python/m5/objects/Bus.mpy:
    Use the new Latency and Frequency types where we can

--HG--
extra : convert_revision : b3cff6020db83fb819507c348451c98697d1cf27