[media] drxk_hard.h: don't use more than 80 columns

X-Patchwork-Delegate: mchehab@redhat.com
Almost all 80-col warnings are related to comments. There's
one, however, that it is due to a one-line enum declaration
for enum agc_ctrl_mode.
Break it into one line per enumered data.

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