media: stv0900_core: remove redundant assignment to variables mclk, div and ad_div

The variables mclk, div and ad_div are being assigned with a values
that are never read and are being updated later with a new values.
The assignments are redundant and can be removed.

Addresses-Coverity: ("Unused value")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>