ethernet: arc: ARC_EMAC and EMAC_ROCKCHIP should depend on HAS_DMA

If NO_DMA=y:

    drivers/built-in.o: In function `arc_emac_tx_clean':
    emac_main.c:(.text+0x2decde): undefined reference to `dma_unmap_single'
    drivers/built-in.o: In function `arc_emac_rx':
    emac_main.c:(.text+0x2dee1c): undefined reference to `dma_unmap_single'
    emac_main.c:(.text+0x2dee72): undefined reference to `dma_map_single'
    emac_main.c:(.text+0x2dee7e): undefined reference to `dma_mapping_error'
    drivers/built-in.o: In function `arc_emac_probe':
    (.text+0x2df2ee): undefined reference to `dmam_alloc_coherent'
    drivers/built-in.o: In function `arc_emac_open':
    emac_main.c:(.text+0x2df6d8): undefined reference to `dma_map_single'
    emac_main.c:(.text+0x2df6e4): undefined reference to `dma_mapping_error'
    drivers/built-in.o: In function `arc_emac_tx':
    emac_main.c:(.text+0x2df9e4): undefined reference to `dma_map_single'
    emac_main.c:(.text+0x2df9f0): undefined reference to `dma_mapping_error'

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