net: ipa: rename ipa_clock_* symbols

Rename a number of functions to clarify that there is no longer a
notion of an "IPA clock," but rather that the functions are more
generally related to IPA power management.

  ipa_clock_enable() -> ipa_power_enable()
  ipa_clock_disable() -> ipa_power_disable()
  ipa_clock_rate() -> ipa_core_clock_rate()
  ipa_clock_init() -> ipa_power_init()
  ipa_clock_exit() -> ipa_power_exit()

Rename the ipa_clock structure to be ipa_power.  Rename all
variables and fields using that structure type "power" rather
than "clock".

Rename the ipa_clock_data structure to be ipa_power_data, and more
broadly, just substitute "power" for "clock" in places that
previously represented things related to the "IPA clock".

Update comments throughout.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>