pmdomain: imx: gpcv2: Discard pm_runtime_put() return value

Passing pm_runtime_put() return value to the callers is not particularly
useful.

Returning an error code from pm_runtime_put() merely means that it has
not queued up a work item to check whether or not the device can be
suspended and there are many perfectly valid situations in which that
can happen, like after writing "on" to the devices' runtime PM "control"
attribute in sysfs for one example.

Accordingly, update imx_pgc_domain_suspend() to simply discard the
return value of pm_runtime_put() and always return success to the
caller.

This will facilitate a planned change of the pm_runtime_put() return
type to void in the future.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peng Fan <peng.fan@nxp.com>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://patch.msgid.link/15658107.tv2OnDr8pf@rafael.j.wysocki