[PPC64] pseries llan: fix MAC address

[luporl]

Summary

There was an issue in pseries llan driver, that resulted in the first 2 bytes of the MAC address getting stripped, and the last 2 being always 0.

In most cases the network interface still worked, despite the MAC being different of what was specified to QEMU, but when some other host or DHCP server expected a specific MAC, this would fail.

This change fixes this by shifting right by 2 the local-mac-address read from device tree, if its length is 6 instead of 8, as observed in QEMU DT, that always presents a 6 bytes value for this property.

[alfredo]

This fixes https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=237471

[jhibbits]

sys/powerpc/pseries/phyp_llan.c

173

You can simply use memmove() or bcopy() here. Doesn't really make a significant difference, though. I think gcc and clang will both degenerate this into the equivalent loop, or a more optimized form.

[luporl]

• Address jhibbits comments

[luporl]

sys/powerpc/pseries/phyp_llan.c

173

Right.