V4L/DVB (13910): cx18: Fix set indextable command to properly select I/P/B index entries

The CX18_CPU_SET_INDEXTABLE command was being called with the wrong number
of arguments causing the index table frame type selection mask to be set wrong.
Now the IDX stream properly sends entries for I, P, and B frames.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>