net: stmmac: Fix descriptors address being in > 32 bits address space

Commit a993db88 ("net: stmmac: Enable support for > 32 Bits
addressing in XGMAC"), introduced support for > 32 bits addressing in
XGMAC but the conversion of descriptors to dma_addr_t was left out.

As some devices assing coherent memory in regions > 32 bits we need to
set lower and upper value of descriptors address when initializing DMA
channels.

Luckly, this was working for me because I was assigning CMA to < 4GB
address space for performance reasons.

Fixes: a993db88

 ("net: stmmac: Enable support for > 32 Bits addressing in XGMAC")
Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>