net: dsa: use NL_SET_ERR_MSG_WEAK_MOD() more consistently

Now that commit 028fb19c

 ("netlink: provide an ability to set
default extack message") provides a weak function that doesn't override
an existing extack message provided by the driver, it makes sense to use
it also for LAG and HSR offloading, not just for bridge offloading.

Also consistently put the message string on a separate line, to reduce
line length from 92 to 84 characters.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20230202140354.3158129-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>