drm/vc4: hdmi: Remove redundant HSM clk enable/disable in detect

Our detect function calls pm_runtime_resume_and_get() and
pm_runtime_put() to make sure the device is properly powered before
trying to access the controller.

However, it also makes sure the HSM clock is properly enabled (and
disabled), which is redundant with what runtime_pm is doing already.
Let's just remove it.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>