Fix events not being set for the cycle counter

A start and stop event must be set for the NPU's cycle counter for it
to know when it should start and stop counting. The driver did not set
these events so the cycle counter didn't work as expected.

Change-Id: I768d46085f51d2ffe4d8f789d5156eb5b660320d
Signed-off-by: Mikael Olsson <mikael.olsson@arm.com>