drm/amdgpu: Fix potential double free and null pointer dereference

In amdgpu_get_xgmi_hive(), we should not call kfree() after
kobject_put() as the PUT will call kfree().

In amdgpu_device_ip_init(), we need to check the returned *hive*
which can be NULL before we dereference it.

Signed-off-by: Liang He <windhl@126.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>