net/hsr: Remove unused function declarations

commit f421436a

 ("net/hsr: Add support for the High-availability Seamless Redundancy protocol (HSRv0)")
introducted these but never implemented.

Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20230729123456.36340-1-yuehaibing@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>