hwmon: (gsc-hwmon) constify read-only struct regmap_bus

`gsc_hwmon_regmap_bus` 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/20240705-hwmon-const-regmap-v1-1-7cde543ba818@gmail.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>