starfire: clean up dma_addr_t size test

Now we have CONFIG_ARCH_DMA_ADDR_T_64BIT. We can fix the hacky
dma_addr_t size test cleanly.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>