firmware: raspberrypi: register clk device

Commit 91f2cf4a upstream.

Since clk-raspberrypi is tied to the VC4 firmware instead of particular
hardware it's registration should be performed by the firmware driver.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>