PM / Domains: Remove redundant wrapper functions for system PM

Due to the previous changes in genpd, which removed the suspend_power_off
flag, several of the system PM callbacks no longer do any additional
checks but only invoke corresponding pm_generic_* helper functions.

To clean up the code, drop these wrapper functions as they have
become redundant. Instead, assign the system PM callbacks directly
to the pm_generic_*() helper functions.

While changing this, it has bocame clear that some of the current
system PM callbacks in genpd invoke wrong driver callbacks. For
example, the genpd's ->restore() callback invokes pm_generic_resume(),
while that should be pm_generic_restore(). Fix that as well.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>