qcacld-3.0: Add support for thermal mitigation after SSR

Wlan driver is not caching the thermal mitigation level
configured by framework. As a result after ssr thermal
level is not send to fw.

Fix, to cache the thermal level in the driver and apply
it after ssr.

Change-ID: I7ede84a11149e093b6a674c3a72f0aeb54a980db
CRs-Fixed: 2678533