diag: Prevent out-of-bound access while processing non-hdlc pkt

While parsing non-hdlc packet buffer length passed to hdlc
recovery is not updated after parsing partial packet, Which
can lead to out-of-bound access. The patch passes the updated
buffer length for the same.

Change-Id: I5596f8c5a72680684c9c9056dccaf33e3c36832c
Signed-off-by: Hardik Arya <harya@codeaurora.org>