selftests: mlxsw: sch_red_core: Drop two unused variables

These variables are cut'n'pasted from other functions in the file and not
actually used.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>