V4L/DVB (4725): Fix vivi compile on parisc

parisc (and several other architectures) don't have a dma_address in their
sg list.  Use the macro instead.

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>