net: ll_temac: Fix support for little-endian platforms

Both TEMAC and SDMA is big-endian, so make sure that all values in SDMA
buffer descriptors (cmdac_bd) are handled as big-endian, independent of the
host endianness. With all currently supported platforms being big-endian,
this change does not make a change for any of them.

Note, when using app3 and app4 for piggybacking skb pointers there is no
need to care about endianness, as neither TEMAC nor SDMA access app3 and
app4 in TX buffer descriptors.

Signed-off-by: Esben Haabendal <esben@geanix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>