HID: i2c-hid: remove extra .irq field in struct i2c_hid

There is no point in keeping the irq in i2c_hid as it's already
there in client.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Reviewed-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>