drm/vc4: Leverage the load tracker on the BCM2711

The load tracker was initially designed to report and warn about a load
too high for the HVS. To do so, it computes for each plane the impact
it's going to have on the HVS, and will warn (if it's enabled) if we go
over what the hardware can process.

While the limits being used are a bit irrelevant to the BCM2711, the
algorithm to compute the HVS load will be one component used in order to
compute the core clock rate on the BCM2711.

Let's remove the hooks to prevent the load tracker to do its
computation, but since we don't have the same limits, don't check them
against them, and prevent the debugfs file to enable it from being
created.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20211025152903.1088803-8-maxime@cerno.tech