rename RTNH_F_EXTERNAL to RTNH_F_OFFLOAD

RTNH_F_EXTERNAL today is printed as "offload" in iproute2 output.

This patch renames the flag to be consistent with what the user sees.

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --cc include/uapi/linux/rtnetlink.h
Simple merge

diff --cc net/ipv4/fib_trie.c
Simple merge

diff --cc net/switchdev/switchdev.c
Simple merge