proto_register_zbee_zcl_appl_evtalt: correct formatting

The original formatting, besides looking silly, also prevents the function
from being picked up by make-dissector-reg.

Change-Id: I06e37b0e862064275b07976295eca8f0288a0974
Reviewed-on: https://code.wireshark.org/review/3025
Reviewed-by: Anders Broman <a.broman58@gmail.com>