iommu: Expand ftrace events

Identify the domain associated with each map or unmap event for
convienence. Additionally, add a map_sg() event.

Change-Id: I9ddf241ffa6cf519f6abece7b0820640f5ce1975
Signed-off-by: Liam Mark <lmark@codeaurora.org>
Signed-off-by: Patrick Daly <pdaly@codeaurora.org>