types: Remove custom MacAddr type

The standard library has an ether_addr type that does the same job.

Change-Id: I98685b0b60dd07453ae2362adb33e0a7c9c3132c
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/neighbor.cpp b/neighbor.cpp
index 1961ad3..d1b1c46 100644
--- a/neighbor.cpp
+++ b/neighbor.cpp
@@ -50,7 +50,7 @@
         auto [hdr, data] = netlink::extractRtAttr(msg);
         if (hdr.rta_type == NDA_LLADDR)
         {
-            neighbor.mac = mac_address::fromBuf(data);
+            neighbor.mac = copyFrom<ether_addr>(data, "Bad neighbor MAC");
         }
         else if (hdr.rta_type == NDA_DST)
         {