Indicate better width limit for pulsers 5 - 15

[gabrielfedel]

At least on evr-mtca-300 and evr-pci-300-dc the pulsers from 5 to 15 has a smaller limit than the 1-4 (e.g.: https://github.com/epics-modules/mrfioc2/blob/master/evrMrmApp/Db/evr-mtca-300.substitutions#L153 and https://github.com/epics-modules/mrfioc2/blob/master/evrMrmApp/Db/evr-pcie-300dc.substitutions#L139C1-L139C102 )

It would be good to have some limit or alarm to avoid user to use above the limit. Also it would be good to check if others EVRs have the same limitation.