PM: clk: make pm_clk_add_notifier() take a const pointer

The driver core wants to work with const struct bus_type, so there's no
reason that pm_clk_add_notifier() should not also do the same thing,
considering that it just passes the pointer off to the driver core which
is expecting a const *.

Cc: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/2023121922-triumph-exploit-f545@gregkh


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>