diag: Rectify the recovery algorithm in case for raw packet

Currently, while receiving packet in hdlc disabled format, it may
happen that the terminating control character is missing. In that
case the recovery algorithm may hit into infinite loop. This
patch rectifies the error condition.

Change-Id: I50861b94599d50c108cd41c765690b3f6ee0823c
Signed-off-by: Katish Paran <kparan@codeaurora.org>