net: macsec: fix net device access prior to holding a lock

Currently macsec offload selection update routine accesses
the net device prior to holding the relevant lock.
Fix by holding the lock prior to the device access.

Fixes: dcb780fb

 ("net: macsec: add nla support for changing the offloading selection")
Reviewed-by: Raed Salem <raeds@nvidia.com>
Signed-off-by: Emeel Hakim <ehakim@nvidia.com>
Link: https://lore.kernel.org/r/20221211075532.28099-1-ehakim@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>