net: convert dev->rtnl_link_state to a bool

net: convert dev->rtnl_link_state to a bool

netdevice reg_state was split into two 16 bit enums back in 2010
in commit a2835763e130 ("rtnetlink: handle rtnl_link netlink
notifications manually"). Since the split the fields have been
moved apart, and last year we converted reg_state to a normal
u8 in commit 4d42b37def70 ("net: convert dev->reg_state to u8").

rtnl_link_state being a 16 bitfield makes no sense. Convert it
to a single bool, it seems very unlikely after 15 years that
we'll need more values in it.

We could drop dev->rtnl_link_ops from the conditions but feels
like having it there more clearly points at the reason for this
hack.

Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250410014246.780885-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>