selftests: mlxsw: rename tc_flower_restrictions.sh to tc_restrictions.sh

The file is about to contain matchall restrictions too, so change the
name to make it more generic.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>