checkpatch: ignore request to use ether_addr_copy()

The Linux kernel, from which checkpatch originates, contains function
ether_addr_copy() to copy Ethernet MAC addresses, and checkpatch warns
that it should be used in preference to memcpy() where appropriate.
U-Boot doesn't contain ether_addr_copy(), so tell checkpatch not to issue
this warning.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Tested-by: Anand Moon <linux.amoon@gmail.com>
Reviewed-by: Anand Moon <linux.amoon@gmail.com>

.checkpatch.conf

@@ -21,3 +21,7 @@
 
 # Ignore networking block comment style
 --ignore NETWORKING_BLOCK_COMMENT_STYLE
+
+# Ignore "WARNING: Prefer ether_addr_copy() over memcpy() if the Ethernet
+# addresses are __aligned(2)".
+--ignore PREFER_ETHER_ADDR_COPY