[media] it913x-fe: use ARRAY_SIZE() as a cleanup

This code looks suspicious, but it turns out that "nv" is an array of u8
so sizeof() is the same as ARRAY_SIZE().  Using ARRAY_SIZE() is more
readable though.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>