media: cleanup fall-through comments

As Ian pointed out, adding a '-' to the fallthrough seems to meet
the regex requirements at level 3 of the warning, at least when
the comment fits into a single line.

So, replace by a single line the comments that were broken into
multiple lines just to make gcc -Wimplicit-fallthrough=3 happy.

Suggested-by: Ian Arkver <ian.arkver.dev@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>