cnss2: Add new MHI PM states for SSR

PM states are used to control MHI driver. Add new states to
support MHI ramdump collection, kernel panic notification and
PCIe link down notification.

Change-Id: I8d599003e579da021d2b0d08a2120868a54032a8
CRs-fixed: 2021415
Signed-off-by: Yuanyuan Liu <yuanliu@codeaurora.org>