mlxsw: spectrum_qdisc: Pass extack to mlxsw_sp_qevent_entry_configure()

This function will report a new failure in the following patches.
Pass extack so that the failure is explicable.

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>