BugLink: http://bugs.launchpad.net/bugs/1559350

The enums are not necessary and this allows the event values to be
used to construct static strings at compile time.
Signed-off-by: Drew Richardson <drew.richardson@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
(cherry picked from commit f4ab36cb)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>