[media] dvb: dmx.h: don't use anonymous enums

There are several anonymous enums here, used via a typedef.

Well, we don't like typedefs on Kernel, so let's de-anonimize
those enums. Then, latter, we may be able to get rid of the
typedefs, at least from Kernelspace.

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