media: dw2102: Fix null-ptr-deref in dw2102_i2c_transfer()

In the Linux kernel, the following vulnerability has been resolved:

media: dw2102: Fix null-ptr-deref in dw2102_i2c_transfer()

In dw2102_i2c_transfer, msg is controlled by user. When msg[i].buf

is null and msg[i].len is zero, former checks on msg[i].buf would be

passed. Malicious data finally reach dw2102_i2c_transfer. If accessing

msg[i].buf[0] without sanity check, null ptr deref would happen.

We add check on msg[i].len to prevent crash.

Similar commit:

commit 950e252cb469

("[media] dw2102: limit messages to buffer size")