'buf' is malloced in dibusb_rc_query() and should be freed before
leaving from the error handling cases, otherwise it will cause
memory leak.

Fixes: ff1c1235 ("[media] dibusb: handle error code on RC query")
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>