mali_kbase: platform: dvfs: Trace with power/gpu_frequency

Emits trace events when the GPU clocks are changed by our DVFS
implementation, using the power/gpu_frequency tracepoint as
defined by the Mali driver.

Note that this doesn't use the upstream Mali clock rate trace
manager interface and instead calls the tracepoints directly.
Since we use a custom DVFS implementation this approach is
more efficient and provides the same end result.

Bug: 169571973
Signed-off-by: Sidath Senanayake <sidaths@google.com>
Change-Id: Ie1d52947ea9af390327151d9807a27655a06190d