cpufreq: suspend/resume governors with PM notifiers

This patch adds PM notifiers for handling suspend/resume of cpufreq governors.
This is required for early suspend and late resume of governors.

There are multiple reasons that support this patch:
- Firstly it looks very much logical to stop governors when we know we are going
  into suspend. But the question is when? Is PM notifiers the right place?
  Following reasons are the supporting hands for this decision.
- Nishanth Menon (TI) found an interesting problem on his platform, OMAP. His board
  wasn't working well with suspend/resume as calls for removing non-boot CPUs
  was turning out into a call to drivers ->target() which then tries to play
  with regulators. But regulators and their I2C bus were already suspended and
  this resulted in a failure. This is why we need a PM notifier here.
- Lan Tianyu (Intel) & Jinhyuk Choi (Broadcom) found another issue where
  tunables configuration for clusters/sockets with non-boot CPUs was getting
  lost after suspend/resume, as we were notifying governors with
  CPUFREQ_GOV_POLICY_EXIT on removal of the last cpu for that policy and so
  deallocating memory for tunables.

All above problems get fixed with having a PM notifier in place which will stop
any operation on governor. Hence no need to do any special handling of variables
like (frozen) in suspend/resume paths.

Reported-by: Lan Tianyu <tianyu.lan at intel.com>
Reported-by: Nishanth Menon <nm at ti.com>
Reported-by: Jinhyuk Choi <jinchoi at broadcom.com>
Signed-off-by: Viresh Kumar <viresh.kumar at linaro.org>
PM: pm33xx: drop support 'mem' (deepsleep).
Merge branch 'fix/cpufreq-suspend-resume' into MA-E3xx/linux-3.14.y