[media] Docbook/ca.xml: match section ID's with the reference links

Make sure that both ca.h.xml and ca.xml will match the same names for
the sections/links.

This way, it is now possible to identify API spec gaps:

Error: no ID for constraint linkend: ca-pid.
Error: no ID for constraint linkend: ca-pid.
Error: no ID for constraint linkend: CA_RESET.
Error: no ID for constraint linkend: CA_GET_CAP.
Error: no ID for constraint linkend: CA_GET_SLOT_INFO.
Error: no ID for constraint linkend: CA_GET_DESCR_INFO.
Error: no ID for constraint linkend: CA_GET_MSG.
Error: no ID for constraint linkend: CA_SEND_MSG.
Error: no ID for constraint linkend: CA_SET_DESCR.
Error: no ID for constraint linkend: CA_SET_PID.

Basically, in this case, no CA ioctl is described at the specs, and one
file structure (ca-pid) is missing.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>