cnss2: Force firmware assert based on context

Currently MHI force firmware assert API is a blocking call, but
it is not necessary to always post it to the serialized driver
workqueue since it may be delayed by another work in the same
workqueue. Directly call the MHI API to assert firmware if it's
not in atomic context.

Change-Id: Iad7afef47d5e64c049a306d4893a05e4735b1c14
Signed-off-by: Yue Ma <yuem@codeaurora.org>