clk: bcm: rpi: Use clk_hw_register for pllb_arm

clk: bcm: rpi: Use clk_hw_register for pllb_arm

The pllb_arm clock is defined as a fixed factor clock with the pllb clock
as a parent. However, all its configuration is entirely static, and thus we
don't really need to call clk_hw_register_fixed_factor() but can simply call
clk_hw_register() with a static clk_fixed_factor structure.

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>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>