Revert "drm/vc4: hdmi: Fix HSM clock too low on Pi4"

This reverts commit 3bc6a37f.

Commit 3bc6a37f ("drm/vc4: hdmi: Fix HSM clock too low on Pi4") was
introduced to work around an issue partly due to the clk-bcm2835 driver
on the RaspberryPi0-3.

Since we're not using that driver for our HDMI clocks, we can now revert
that inelegant solution.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20230126-rpi-display-fw-clk-cleanup-v1-3-d646ff6fb842@cerno.tech


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