iio: light: cm32181: make cm32181_pm_ops static

This symbol is not used outside of cm32181.c, so marks it static.

Fixes the following sparse warnings:
>> drivers/iio/light/cm32181.c:508:1: sparse: sparse: symbol 'cm32181_pm_ops'
was not declared. Should it be static?
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: sunliming <sunliming@kylinos.cn>
Link: https://lore.kernel.org/r/20220815012930.150078-1-sunliming@kylinos.cnSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/cm32181.c

@@ -505,7 +505,7 @@ static int cm32181_resume(struct device *dev)
 					 cm32181->conf_regs[CM32181_REG_ADDR_CMD]);
 }
 
-DEFINE_SIMPLE_DEV_PM_OPS(cm32181_pm_ops, cm32181_suspend, cm32181_resume);
+static DEFINE_SIMPLE_DEV_PM_OPS(cm32181_pm_ops, cm32181_suspend, cm32181_resume);
 
 static const struct of_device_id cm32181_of_match[] = {
 	{ .compatible = "capella,cm3218" },