Now that all the SCMI driver users have been migrated to the new interface
remove the legacy interface and all the transient code.

Link: https://lore.kernel.org/r/20210316124903.35011-20-cristian.marussi@arm.comTested-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NCristian Marussi <cristian.marussi@arm.com>
Signed-off-by: NSudeep Holla <sudeep.holla@arm.com>