clk: bcm: rpi: Create a data structure for the clocks

So far the driver has really only been providing a single clock, and stored
both the data associated to that clock in particular with the data
associated to the "controller".

Since we will change that in the future, let's decouple the clock data from
the provider data.

Cc: Michael Turquette <mturquette@baylibre.com>
Cc: linux-clk@vger.kernel.org
Acked-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Tested-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/ee7f508db226214fab4add7f93a351f4137c86a1.1592210452.git-series.maxime@cerno.tech


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