V4L/DVB (5592): DMA: Correctly free resources on error, sync PCI streamed data

I added saa7146_vmalloc_destroy_pgtable() which frees the resources
allocated by saa7146_vmalloc_build_pgtable() and updated the callers in
budget-core.c and av7110.c. I have also been through the updated
functions and updated the error paths to ensure they free all allocated
resources on error.
I also realised that there are other callers to saa7146_pgtable_free()
which did not have any sg DMA mapped so it seems wrong to add the
pci_unmap_sg() into that function. Instead I created
saa7146_vmalloc_destroy_pgtable() to do this.
Also included in this patch are the previous fixes for pci_unmap_sg()
and syncing the PCI streamed data to work with a SWIOTLB and match the
requirements documented in DMA-API.txt.

Signed-off-by: Jon Burgess <jburgess777@googlemail.com>
Signed-off-by: Oliver Endriss <o.endriss@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>