media: ddbridge: remove unreachable code

>From smatch:

  drivers/media/pci/ddbridge/ddbridge-core.c:3490 snr_store() info: ignoring unreachable code.

In fact, the function immediately returns zero, so remove it and update
ddb_attrs_snr[] to not reference it anymore.

Cc: Ralph Metzler <rjkm@metzlerbros.de>
Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Tested-by: Richard Scobie <r.scobie@clear.net.nz>
Tested-by: Jasmin Jessich <jasmin@anw.at>
Tested-by: Dietmar Spingler <d_spingler@freenet.de>
Tested-by: Manfred Knick <Manfred.Knick@t-online.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>