To support the ability to implement PM hibernation code as modules
the hibernation_set_ops function requires to be exported.

Similar solution already available for suspend_set_ops
(please refer to commit a5e4fd87).
Signed-off-by: NLeonardo Potenza <leonardo.potenza@intel.com>
Signed-off-by: NEdwin Verplanke <edwin.verplanke@intel.com>
Reviewed-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>