Deny led breathing on hammerhead

Changing led parameters on hammerhead is slow enough to make mce cpu
bound when sw breathing is used.

Do not allow hammerhead backend to breathe.

Add new plugin interface function mce can use to query whether breathin
can be enabled or not.

[hybris.so] Deny led breathing on hammerhead. Fixes JB#21845
Merge pull request #13 from spiiroin/can_breathe

Deny led breathing on hammerhead