ide-cd: fix ACER/AOpen 24X CDROM speed reporting on big-endian machines

* Fix ACER/AOpen 24X CDROM speed reporting on big-endian machines
  by adding missing le16_to_cpu() calls.

While at it:
* Replace ntohs() by be16_to_cpu().

Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>