iio: imu: inv_icm42600: Use devm_regulator_get_enable() for vdd regulator

iio: imu: inv_icm42600: Use devm_regulator_get_enable() for vdd regulator

The vdd regulator is not used for runtime power management, so it does
not need explicit enable/disable handling.
Use devm_regulator_get_enable() to let the regulator be managed
automatically by devm.

This simplifies the code by removing the manual enable and cleanup
logic.

Signed-off-by: Sean Nyekjaer <sean@geanix.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20250901-icm42pmreg-v3-4-ef1336246960@geanix.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>