Firmware should mask OptoHybrids without enabled VFAT
During an automatic VFAT masking iteration (either in software or firmware), it can happen that all VFATs for a given OptoHybrid end up being masked. If the OptoHybrid remains enabled in the input enable mask, this will create deadtime at high L1A rate due to the main event builder timeout being triggered for every L1A.
Instead, the firmware should automatically disable OptoHybrids for which all VFAT are masked. Different options are possible, but it should be reported to the user via registers and in the data format. A new field can be added in the data format (if space is available) or the corresponding chambers can be preset in timeout (i.e. the flag is raised without waiting for the timeout to actually happen).
As described in #24, the effects should be only on the event building, not on all kinds of communication.