net: mvpp2: set dma mask and coherent dma mask on PPv2.2

On PPv2.2, the streaming mappings can be anywhere in the first 40 bits
of the physical address space. However, for the coherent mappings, we
still need them to be in the first 32 bits of the address space,
because all BM pools share a single register to store the high 32 bits
of the BM pool address, which means all BM pools must be allocated in
the same 4GB memory area.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: David S. Miller <davem@davemloft.net>