clk: bcm: rpi: Create helper to retrieve private data

clk: bcm: rpi: Create helper to retrieve private data

The RaspberryPi firmware clocks driver uses in several instances a
container_of to retrieve the struct raspberrypi_clk_data from a pointer
to struct clk_hw. Let's create a small function to avoid duplicating it
all over the place.

Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://lore.kernel.org/r/20250116-bcm2712-clk-updates-v1-4-10bc92ffbf41@raspberrypi.com
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>