Import CRC16 calculation routines from Linux kernel v5.10:

  include/linux/crc-ccitt.h
  lib/crc-ccitt.c

to QEMU:

  include/qemu/crc-ccitt.h
  util/crc-ccitt.c

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20210123104016.17485-7-bmeng.cn@gmail.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
[PMD: Restrict compilation to system emulation]
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>