V4L/DVB (6290): remove videobuf_set_pci_ops

Before the videobuf redesign, a procedure for re-using videobuf without PCI
scatter/gather where provided by changing the pci-dependent operations by
other operations.

With the newer approach, those methods are obsolete and can safelly be removed.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>