The check for the existence of callbacks before using them implies that
this happens and is supported. There are no devices without
enable/disable callbacks, and it wouldn't be possible to add a new
working device without adding them either, so just remove them.

Furthermore, there are more callbacks than just enable and disable that
are already used unguarded in other places.

The comment about new session compatibility doesn't seem to match up to
the line of code that it's on so remove it. I think it's alluding to the
fact that sinks will check if they were already enabled via sysfs or
Perf and fail the enable. But there are more detailed comments at those
places, and this one isn't very useful.
Signed-off-by: James Clark <james.clark@arm.com>
Link: https://lore.kernel.org/r/20240129154050.569566-4-james.clark@arm.comSigned-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>