HID: i2c-hid: fix memory corruption due to missing hid declaration

HID descriptors contains 4 bytes of reserved field.
The previous implementation was overriding the next fields in struct i2c_hid.

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>