media: ddbridge: link structure access cosmetics in ddb_port_probe()

Throughout the function, dev->link[l] is used several times. Unclutter
this a bit by declaring a ddb_link var at the top of the function, assign
the address of dev->link[l] to it and use that var to access the link[]
struct member.

Picked up from the upstream dddvb GIT.

Signed-off-by: Daniel Scheller <d.scheller@gmx.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>