mlxsw: spectrum_router: Remove deadcode in mlxsw_sp_rif_mac_profile_find

The function idr_for_each_entry() already checks that the next entry in
the IDR is not NULL.

Therefore, checking that again in every iteration leads to deadcode.

Remove the unnecessary check in order to avoid that.

Addresses-Coverity: ("Logically dead code")
Signed-off-by: Danielle Ratson <danieller@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>