pmdomain: de-constify fields struct dev_pm_domain_attach_data

It doesn't really make sense to keep u32 fields to be marked as const.
Having the const fields prevents their modification in the driver.
Instead the whole struct can be defined as const (if it is constant).

Fixes: 161e16a5e50a ("PM: domains: Add helper functions to attach/detach multiple PM domains")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>