HID: ft260: check data size in ft260_smbus_write()

The SMbus block transaction limits the number of bytes transferred to 32,
but nothing prevents a user from specifying via ioctl a larger data size
than the ft260 can handle in a single transfer.

i2cdev_ioctl_smbus()
   --> i2c_smbus_xfer
       --> __i2c_smbus_xfer
           --> ft260_smbus_xfer
               --> ft260_smbus_write

This patch adds data size checking in the ft260_smbus_write().

Fixes: 98189a0adfa0 ("HID: ft260: add usb hid to i2c host bridge driver")
Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>