net: hsr: convert to use new timer APIs

del_timer() and del_timer_sync() have been renamed to timer_delete()
and timer_delete_sync().

Inconsistent API usage makes the code a bit confusing, so replace with
the new APIs.

No functional changes intended.

Signed-off-by: Yu Liao <liaoyu15@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>