Pull Operating Performance Points (OPP) library changes for v4.18
from Viresh Kumar.

* 'opp/genpd-pstate-updates' of git://git.kernel.org/pub/scm/linux/kernel/git/vireshk/pm:
  PM / OPP: Remove dev_pm_opp_{un}register_get_pstate_helper()
  PM / OPP: Get performance state using genpd helper
  PM / Domain: Implement of_genpd_opp_to_performance_state()
  PM / Domain: Add support to parse domain's OPP table
  PM / Domain: Add struct device to genpd
  PM / OPP: Implement dev_pm_opp_get_of_node()
  PM / OPP: Implement of_dev_pm_opp_find_required_opp()
  PM / OPP: Implement dev_pm_opp_of_add_table_indexed()
  PM / OPP: "opp-hz" is optional for power domains
  PM / OPP: dt-bindings: Make "opp-hz" optional for power domains
  PM / OPP: dt-bindings: Rename "required-opp" as "required-opps"
  soc/tegra: pmc: Don't allocate struct tegra_powergate on stack