Device ("ifname" UCI option) doesn't depend on protocol so there is no
need to hide / reset it on protocol change.
While at it drop names of two removed inputs (dead code).
Fixes: ec020cee0c44 ("luci-mod-network: drop support for *editing* legacy bridges")
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
(cherry picked from commit 907b4222f70b3351d590d8a2e35c21a4ae07db8d)