Convert all refactored events registration routines to use protocol handles. In order to maintain bisectability and to allow protocols and drivers to be later ported to the new protocol handle interface one by one, introduce here also some transient code that will be removed later in order to ease such transition. Link: https://lore.kernel.org/r/20210316124903.35011-8-cristian.marussi@arm.com Tested-by: Florian Fainelli <f.fainelli@gmail.com> Signed-off-by: Cristian Marussi <cristian.marussi@arm.com> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>