vxlan: Cleanup IFLA_VXLAN_PORT_RANGE entry in vxlan_get_size()

vxlan: Cleanup IFLA_VXLAN_PORT_RANGE entry in vxlan_get_size()

This patch is basically a followup to commit 4e4b1798cc90 ("vxlan: Add
missing entries to vxlan_get_size()"). All of the attributes in
vxlan_get_size() appear in the same order that they are filled in
vxlan_fill_info() except for IFLA_VXLAN_PORT_RANGE. For consistency, move
that entry to match its order and add a comment, like for all other
entries.

Signed-off-by: Benjamin Poirier <bpoirier@nvidia.com>
Link: https://lore.kernel.org/r/20231027184410.236671-1-bpoirier@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>