missing precision option for values with default precision 0

[ghoz]

Following up on #8792

It looks like we are skipping precision if the default precision is 0 which is the case for ac_frequency

zigbee-herdsman-converters/src/index.ts

Lines 358 to 360 in c4499e6

	if (utils.calibrateAndPrecisionRoundOptionsDefaultPrecision[expose.name] !== 0) {
	definition.options.push(exposesLib.options.precision(expose.name));
	}

short term thinking :
change the default ac_frequency precision to 2 as it makes more sense (grid opreators are supposed to keep the frequency very tightly around the standard value).

propper fixing : move to -1 for no precision rather than 0? as this most likely impacts others valuesbwith default prexision of 0 ...
does a -1 precision makes sense (rounding to 10s ?)