cnss2: Add support for sending athdiag read/write messages

Add support for sending athdiag read/write commands to firmware
through QMI. This can enhance the runtime debugging capability
for WLAN hardware.

Change-Id: Idbc5f0d02969c5659cee378fdcddab0f64a9310d
Signed-off-by: Yue Ma <yuem@codeaurora.org>