devlink: fix netns refcount leak in devlink_nl_cmd_reload()

In the Linux kernel, the following vulnerability has been resolved:

devlink: fix netns refcount leak in devlink_nl_cmd_reload()

While preparing my patch series adding netns refcount tracking,

I spotted bugs in devlink_nl_cmd_reload()

Some error paths forgot to release a refcount on a netns.

To fix this, we can reduce the scope of get_net()/put_net()

section around the call to devlink_reload().