For 4.14 kernel, it turns out that the vdoa driver cannot use module_init(), otherwise, the driver's probe function cannot be called. Using subsys_initcall() makes the probe function be successfully called, just like the ipu_common driver. Note that the mxc_ipu.o object consists of the ipu_common driver and the vdoa driver. Signed-off-by: Liu Ying <victor.liu@nxp.com>