net: pxa168_eth: PXA168_ETH should depend on HAS_DMA

If NO_DMA=y:

drivers/built-in.o: In function `rxq_deinit':
pxa168_eth.c:(.text+0x2a2f2e): undefined reference to `dma_free_coherent'
drivers/built-in.o: In function `txq_reclaim':
pxa168_eth.c:(.text+0x2a3044): undefined reference to `dma_unmap_single'
drivers/built-in.o: In function `txq_deinit':
pxa168_eth.c:(.text+0x2a310a): undefined reference to `dma_free_coherent'
drivers/built-in.o: In function `txq_init':
pxa168_eth.c:(.text+0x2a3226): undefined reference to `dma_alloc_coherent'
drivers/built-in.o: In function `rxq_init':
pxa168_eth.c:(.text+0x2a32d4): undefined reference to `dma_alloc_coherent'
drivers/built-in.o: In function `init_hash_table':
pxa168_eth.c:(.text+0x2a3354): undefined reference to `dma_alloc_coherent'
drivers/built-in.o: In function `rxq_refill':
pxa168_eth.c:(.text+0x2a345a): undefined reference to `dma_map_single'
drivers/built-in.o: In function `rxq_process':
pxa168_eth.c:(.text+0x2a39cc): undefined reference to `dma_unmap_single'
drivers/built-in.o: In function `pxa168_eth_remove':
pxa168_eth.c:(.text+0x2a3b84): undefined reference to `dma_free_coherent'
drivers/built-in.o: In function `pxa168_eth_start_xmit':
pxa168_eth.c:(.text+0x2a3e8a): undefined reference to `dma_map_single'

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: David S. Miller <davem@davemloft.net>