[media] v4l: vb2-dma-contig: let mmap method to use dma_mmap_coherent call

Let mmap method to use dma_mmap_coherent call.  Moreover, this patch removes
vb2_mmap_pfn_range from videobuf2 helpers as it was suggested by Laurent
Pinchart.  The function is no longer used in vb2 code.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

include/media/videobuf2-memops.h

@@ -33,11 +33,6 @@ extern const struct vm_operations_struct vb2_common_vm_ops;
 int vb2_get_contig_userptr(unsigned long vaddr, unsigned long size,
 			   struct vm_area_struct **res_vma, dma_addr_t *res_pa);
 
-int vb2_mmap_pfn_range(struct vm_area_struct *vma, unsigned long paddr,
-				unsigned long size,
-				const struct vm_operations_struct *vm_ops,
-				void *priv);
-
 struct vm_area_struct *vb2_get_vma(struct vm_area_struct *vma);
 void vb2_put_vma(struct vm_area_struct *vma);