sparc32: add offset in pci_map_sg()

Add sg->offset to sg->dvma_address in pci_map_sg() on sparc32.  Without the
offset, transfers to buffers that do not begin on a page boundary will not
work as expected.

Signed-off-by: Jan Andersson <jan.andersson@ieee.org>
Acked-By: David Miller <davem@davemloft.net>