net: designware: make alt/enhanced descriptor runtime configurable
Instead of hardcoding the alternate/enhanced descriptor layout make
it configurable during runtime. This is based on the value of the
enh_desc variable which is currently hardcoded to zero. This should
be configurable via device_id in the future. Since currently we have
no in tree user of this driver this currently doesn't hurt.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>