[media] media: vb2: dma contig allocator: use dma_addr instread of paddr

Use the correct 'dma_addr' name for the buffer address. 'paddr' suggested
that this is the physical address in system memory. For most ARM platforms
these two are the same, but this is not a generic rule. 'dma_addr' will
also point better to dma-mapping api.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
CC: Pawel Osciak <pawel@osciak.com>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>