drm/amdgpu: kfd_initialized can be static

Fixes: c7651b73 ("drm/amdgpu: Fix handling of KFD initialization failures")
Signed-off-by: kernel test robot <lkp@intel.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>