[media] dvb_ca_en50221.h: Make checkpatch.pl happy

There are several CodingStyle violations at the DVB code. While
we won't be fixing them as a hole, let's fix at least the
headers, as we're touching on them already in order to properly
document them.

No functional changes.

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