sysutils/cdrdao: Fix zero length DMA with ata(4)

Fix zero length DMA transfer attempted failures with the ata(4) driver.
This does not seem to affect users of the ahci(4) driver.

While here, convert bzero/bcopy to memset/memmove, respectively.

PR: 277115
Reported by: Benjamin Jacobs <freebsd@dev.thsi.be>