ipv6: raw: remove useless input parameter in rawv6_get/seticmpfilter

The input parameter 'level' in rawv6_get/seticmpfilter is not used.
Therefore, remove it.

Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>