diag: Add diag support for NPU

Add support for diag communication between apps and
npu to send/receive diag traffic.

Change-Id: I78dd00928a4c155c794bc3334f46c2e0c55a6f77
Signed-off-by: Sreelakshmi Gownipalli <sgownipa@codeaurora.org>
Signed-off-by: Manoj Prabhu B <bmanoj@codeaurora.org>