Add flush for offline devices. Change-Id: I16cc60cc26cfa225a80aa8627d4148568329d676 Signed-off-by: Junzhe Zou <jnzhezou@codeaurora.org> Signed-off-by: Suresh Vankadara <svankada@codeaurora.org> Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org> Signed-off-by: Rajakumar Govindaram <rajakuma@codeaurora.org>