ARM: shmobile: Lager: set proper DMA masks for Ether device

Ether MAC is a DMA-capable device and so should have 'dev.dma_mask' and
'dev.coherent_dma_mask' fields set properly, to reflect 32-bit DMA addressing
ability.

Currently, the code works without DMA masks but as we would have to enable
CONFIG_HIGHMEM to access the full board memory in the future, when support for
NETIF_F_SG would be added to the 'sh_eth' driver as well, the correct DMA masks
should start to matter...

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>