The default iPXE settings of 8 (RXD) and 16 (TXD) lead to issues when
AMT is enabled. In most other OS drivers those descriptors are set
to 256, let us do the same. This should fix all observed issues wrt.
AMT.
Fixes#2108.
Inspired by the mailing-list posting [1], this commit removes the
MAC/PHY reset for all Intel cards and effectively prevents the bandwidth
drop to 10 MBit/s (e.g., on i217lm). I understand it as preliminary fix
for practical reasons - a real fix would be to update the ipxe port and
monitor for more postings like the one mentioned.
[1] http://lists.ipxe.org/pipermail/ipxe-devel/2015-December/004511.html
