PM: domains: use dev_err_probe() to simplify error handling

dev_err_probe() can reduce code size, makes the code easier to read
and has the added benefit of recording the defer reason for later
read out. Use it where appropriate.

This also fixes an issue, where an error message in __genpd_dev_pm_attach
was not terminated by a line break.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>