[media] go7007: fix invalid use of sizeof in go7007_usb_i2c_master_xfer()

sizeof() when applied to a pointer typed expression gives the
size of the pointer, not that of the pointed data.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>