V4L/DVB: drivers/media: Make static data tables and strings const

Making static data const avoids allocation of additional r/w memory and
reduces initialisation time.  It also provides some additional opportunities
for compiler optimisations.

Signed-off-by: Lawrence Rust <lvr@softsystem.co.uk>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>