defconfig: mdm9630: Enable CNSS platform driver

Enable CNSS platform driver for mdm9630.
Platform driver takes care of following items for QCA6174.
    1. Bring-up QCA6174
    2. Subsystem Restart support

Change-Id: Iffa6143d5788c8edb730638a3ab03c12df833fbc
Signed-off-by: Prashanth Bhatta <bhattap@codeaurora.org>