In the transmit interrupt handler, do not unnecessarily synchronize all the descriptors for a buffer chain.  Just synchronize the last one, which has the interesting stuff.
In the transmit interrupt handler, do not unnecessarily synchronize
all the descriptors for a buffer chain.  Just synchronize the last
one, which has the interesting stuff.

We still synchronize all the descriptors for the buffer chain if
super-verbose debugging is enabled, since the driver will print
all the descriptors for the chain.

Delay for tens of milliseconds lot after writing the Network Access
Register.  This is what the reference driver does, we can probably
lower the delays later.

From NetBSD (dyoung)

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars