cnss2: Add pm control in workqueue

Add pm control when processing works from workqueue, which can prevent
system suspend while platform driver is in the middle of handling an
event.

CRs-Fixed: 2011680
Change-Id: Iecdea94f4f6509b512261f252b0a43152cf0724e
Signed-off-by: Yuanyuan Liu <yuanliu@codeaurora.org>