[sysfs-led] Add diagnostic logging
[sysfs-led] Add diagnostic logging

To improve visibility to led control flow from mce side logic
down to backend level.

Signed-off-by: Simo Piiroinen <6d5e5360bed3d486f7d9fb26b0f737f7d4fd45ee@jollamobile.com>

nemomobile/mce-plugin-libhybris,nemomobile/mce-plugin-libhybris,spiiroin/mce-plugin-libhybris,spiiroin/mce-plugin-libhybris,spiiroin/mce-plugin-libhybris,nemomobile/mce-plugin-libhybris,spiiroin/mce-plugin-libhybris,nemomobile/mce-plugin-libhybris