V4L/DVB: saa7115: enable anti-alias filter

This patch enables the anti-alias filter, which was originally enabled for
the saa7113, but the saa7115_init_misc was trampling the value.  Without this
patch, there would be visible vertical bands in the chroma.

Thanks to Andy Walls for helping test this change against other ivtv products.

This work was sponsored by EyeMagnet Limited.

Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>