net: ieee802154: adf7242: drop owner from driver

Core already sets owner in spi_driver.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: David S. Miller <davem@davemloft.net>