alc(4): add support for Mikrotik 10/25G NIC

alc(4): add support for Mikrotik 10/25G NIC

The new Mikrotik 10/25G NIC is mostly compatible with AR8151 hardware,
with few exceptions:

* card supports only 32bit DMA operations
* card does not support write-one-to-clear semantics for interrupt status
  register
* MDIO operations can take longer to complete

This patch adds support for Mikrotik 10/25G NIC to the alc driver
while maintaining support for all earlier HW.

The patch was tested with FreeBSD main branch as of commit
f4b38c360e63a6e66245efedbd6c070f9c0aee55

This was tested on Intel i7-4790K system with Mikrotik 10/25G NIC.
This was tested on Intel i7-4790K system with RB44Ge (AR8151 based 4-port NIC)
to verify backwards compatibility.

PR:	256000
Submitted by:	 Gatis Peisenieks  <gatis@mikrotik.com>
MFC after:	1 week