Convert large numbers of instances of overt driver_t structures to using
the DEFINE_CLASS_0() macro. Greater consistency should reduce future
errors. Convert several uses of '{ 0, 0 }' driver method list ends to
DEVMETHOD_END macro.
Small amounts of similar cleanup to similar macros. The opal_sensor
module had omitted the sentinal from the table. That had likely been
functioning due to dumb luck for some time.