clk: bcm: rpi: Set a default minimum rate

The M2MC clock provides the state machine clock for both HDMI
controllers.

However, if no HDMI monitor is plugged in at boot, its clock rate will
be left at 0 by the firmware and will make any register access end up in
a CPU stall, even though the clock was enabled.

We had some code in the HDMI controller to deal with this before, but it
makes more sense to have it in the clock driver. Move it there.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20220225143534.405820-10-maxime@cerno.tech


Signed-off-by: Stephen Boyd <sboyd@kernel.org>