cnss2: Add CNSS_BUS_EVENT to report bus info

CNSS_BUS_EVENT type added to report bus related info to
CLD driver.
Currently only PCIe's link down event taken care.

Change-Id: Ia18ce1b9ca8d0641e62271d645f1c87461029a26
Signed-off-by: Lin Bai <lbai@codeaurora.org>