handle fixed-link configuration in the device tree.

handle fixed-link configuration in the device tree.

if fixed-link is present, populate the interface baudrate and link
status (full duplex or half duplex), and then call the statch handler
to apply that config to the MAC. if fixed-link is specified then
do not attach a phy.

note that phy lookup and reset still occurs in case the device tree
still uses the deprecated snps,reset-gpio properties. the fixed
link port on the bpi r2 pro is connected to a switch chip (which
is not really a phy) that needs needs a reset provided by the
snps,reset-gpio handling. an improved device tree would have the
reset properties on the switch node so it could do its own reset,
but we can't have nice things can we?

tested on a nanopi r5s, which has a phy but no fixed-link config,
and a banana pi bpi-r2 pro, which has both (cos it has two dwqes,
one with a phy and one without).