slimbus: Sequentialize the device state notifications

During subsystem restart, queue all the device state notification work
in the same workqueue. This ensures that those notifications reach the
slave drivers in the expected order.

CRs-Fixed: 2139743
Change-Id: I3cdfbdd7ca500c5470c6c29b3a16780dcd2208dc
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>