Update synapse driver only if new exc or inh bit is set
Update synapse driver only if new exc or inh bit is set

* If both bits are cleared, the drivers are not changed
Change-Id: I98cd1d530a910564ce03c8710319db8c38f6c293

electronicvisions/spikeyhal,electronicvisions/spikeyhal,electronicvisions/spikeyhal,electronicvisions/spikeyhal