clk: xilinx: Constify struct regmap_config

`vcu_settings_regmap_config` is not modified and can be declared as
const to move its data to a read-only section.

Signed-off-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>
Link: https://lore.kernel.org/r/20240703-clk-const-regmap-v1-10-7d15a0671d6f@gmail.com


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