This way we do not need to transverse the device tree manually and we
support hot plugged devices.

Also Implement remove callback so the driver can be unloaded
Acked-by: NMichal Simek <michal.simek@xilinx.com>
Signed-off-by: NRicardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>