mlxsw: Remove unused including <generated/utsrelease.h>

Remove including <generated/utsrelease.h> that don't need it.

Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>