Bytes and cycles for prefix opcodes

Some people (on the emudev Discord server) seem to be confused by the fact that the table lists `0xCB` as 1 byte and 4 cycles, while all the `0xCB`-prefixed opcodes in the separate table add that 1 byte and those 4 cycles to their totals.

For example, `RLC B` at `0xCB 0x00` is listed as taking 2 bytes and 8 cycles, but in the main table `PREFIX` at `0xCB` is listed as taking 1 byte and 4 cycles.

That's not incorrect _per se_, since fetching the 1-byte prefix takes 4 cycles, so I'm not sure what the best "solution" would be. Perhaps just a footnote?