Revert "[media] V4L: videobuf, don't use dma addr as physical"

This reverts commit 35d9f510.

Quoth Jiri Slaby:
 "It fixes mmap when IOMMU is used on x86 only, but breaks architectures
  like ARM or PPC where virt_to_phys(dma_alloc_coherent) doesn't work.
  We need there dma_mmap_coherent or similar (the trickery what
  snd_pcm_default_mmap does but in some saner way).  But this cannot be
  done at this phase."

Requested-by: Jiri Slaby <jslaby@suse.cz>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>