Fix a typo which resulted in wrong .read hooks and unset .write
hooks. This made I2C_SMBUS_BLOCK_DATA transfers dereference the
NULL .write hook and Oops.
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Link: https://github.com/openwrt/openwrt/pull/17950
Signed-off-by: Sander Vanheule <sander@svanheule.net>