clk: si570: Use managed `of_clk_add_hw_provider()`

Use the managed `devm_of_clk_add_hw_provider()` instead of
`of_clk_add_hw_provider()`.

This makes sure the provider gets automatically removed on unbind and
allows to completely eliminate the drivers `remove()` callback.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20230410014502.27929-9-lars@metafoo.de


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