media: cx18: use GFP_KERNEL

Pci_driver probe functions aren't called with locks held
and thus don't need GFP_ATOMIC. Use GFP_KERNEL instead.

Problem found with Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>