qcacmn: Move power_gating to centralized power management api.

Upper layers should not need to know about pci specific power management
features.

Change-Id: I841af588246d328f12fa69d8c0394ec1eafaa236
CRs-Fixed: 986480

htc/htc_api.h

@@ -709,7 +709,6 @@ int htc_runtime_suspend(void);
 int htc_runtime_resume(void);
 
 /* Disable ASPM : Disable PCIe low power */
-void htc_disable_aspm(HTC_HANDLE HTCHandle);
 bool htc_can_suspend_link(HTC_HANDLE HTCHandle);
 void htc_vote_link_down(HTC_HANDLE HTCHandle);
 void htc_vote_link_up(HTC_HANDLE HTCHandle);