au1000_eth: stop using virt_to_bus()

The conversion to the dma-mapping API in linux-2.6.11 was incomplete
and left a virt_to_bus() call around. There have been a number of
fixes for DMA mapping API abuse in this driver, but this one always
slipped through.

Change it to just use the existing dma_addr_t pointer, and make it
use the correct types throughout the driver to make it easier to
understand the virtual vs dma address spaces.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Manuel Lauss <manuel.lauss@gmail.com>
Link: https://lore.kernel.org/r/20220607090206.19830-1-arnd@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>