slimbus: Add support for report-absent and device-down notification

device_down callback will be called when the device sends
report-absent message per slimbus specification, or if the device
cannot be reached due to some other reason (e.g. bus going down).
device_up will be called when the device sends reports present again.

Change-Id: Ie48c2e3891b55cb1ec9c675a32cdb0a568fdcc18
Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>
3 files changed