defxx.c: dfx_bus_init() is __devexit not __devinit

 The dfx_bus_uninit() call is called from dfx_unregister() which is
__devexit and which is ultimately the ->remove call for the device.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>