Update LED service bus name

The phosphor-led-sysfs may be changed to run one process for all LEDs.
This is according to this design

https://gerrit.openbmc.org/c/openbmc/docs/+/55230

This patch updates the bus name accordingly for this repo.

It should only be merged after the corresponding change in
phosphor-led-sysfs has been merged.

Change-Id: I5fe64d66caecfe1146d089216902dcb2ec379e82
Signed-off-by: Alexander Hansen <alexander.hansen@9elements.com>