qcwcn: Heap-buffer-overflow in register_monitor_sock() of wifi hal

This changes is to avoid the buffer-overflow in register_monitor_sock()
where "nreg->monsock" is getting filled with the data of length
"ctrl_msg->monsock_len" without the validation of length. Address this
issue by have a length check done before filling the buffer.

Change-Id: I36b7ac274bd4f92eceabd5bd6534c73ae5a9ae73
CRs-Fixed: 2604404