diag: dci: Check for request pkt length being lesser than minimum length

Added checks for DCI request packets to be greater than the minimum
packet length. We would drop the request and print an error otherwise.

CRs-Fixed: 483310
Change-Id: I0d89ded58ee97a08ebe6b06b411ac17d2fcb11df
Signed-off-by: Ravi Aravamudhan <aravamud@codeaurora.org>