Have you tried this?
static const struct device *const pdm_imu_reg = DEVICE_DT_GET(DT_NODELABEL(pdm_imu_pwr));
static const struct device *const rfsw_reg = DEVICE_DT_GET(DT_NODELABEL(rfsw_pwr));
static const struct device *const vbat_reg = DEVICE_DT_GET(DT_NODELABEL(vbat_pwr));
regulator_disable(pdm_imu_reg);
regulator_disable(rfsw_reg);
regulator_disable(vbat_reg);