clk: nodrv: Add a determine_rate hook

The nodrv clock implements a mux with a set_parent hook, but doesn't
provide a determine_rate implementation.

Even though it's a mock clock and the missing function is harmless,
we'll start to require a determine_rate implementation when set_parent
is set, so let's fill it.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20221018-clk-range-checks-fixes-v4-6-971d5077e7d2@cerno.tech


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