[bug report] drm/amd/powerplay: add point check to avoid NULL point hang.

[Dan Carpenter]

Hello Rex Zhu,

The patch 88b8dcbe21fd: "drm/amd/powerplay: add point check to avoid
NULL point hang." from Dec 11, 2015, leads to the following static
checker warning:

	drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/hardwaremanager.c:274 phm_check_smc_update_required_for_display_configuration()
	warn: signedness bug returning '(-22)'

drivers/gpu/drm/amd/amdgpu/../pm/powerplay/hwmgr/hardwaremanager.c
   272  bool phm_check_smc_update_required_for_display_configuration(struct pp_hwmgr *hwmgr)
   273  {
   274          PHM_FUNC_CHECK(hwmgr);

PHM_FUNC_CHECK() has a hiddren -EINVAL return that becomes true when
casted to bool.

   275          if (hwmgr->pp_one_vf)
   276                  return false;
   277  
   278          if (hwmgr->hwmgr_func->check_smc_update_required_for_display_configuration == NULL)
   279                  return false;
   280  
   281          return hwmgr->hwmgr_func->check_smc_update_required_for_display_configuration(hwmgr);
   282  }

regards,
dan carpenter