protected long getDefaultOffsetFromFlat(long flat) {
		if (flat > 0xFFFFFL) {
			return flat - 0xFFFF0;
		}
		return flat & 0xFFFFL;
	}
Given a flat address offset, extract the offset portion assuming the
default segment.
@param flat is the flat offset
@return the offset value
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/address/SegmentedAddressSpace.java