clk: meson: g12: drop use of __clk_lookup()

g12 clock controller used __clk_lookup() to get struct clk from a
struct clk_hw. This type of hack is no longer required as CCF now provides
the necessary functions to get this.

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Link: https://lore.kernel.org/r/20201021162147.563655-4-jbrunet@baylibre.com


Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>