mlxsw: spectrum_router: Remove unused functions

mlxsw: spectrum_router: Remove unused functions

mlxsw_sp_ipip_lb_ul_vr_id() has been unused since 2020's
commit acde33bf7319 ("mlxsw: spectrum_router: Reduce
mlxsw_sp_ipip_fib_entry_op_gre4()")

mlxsw_sp_rif_exists() has been unused since 2023's
commit 49c3a615d382 ("mlxsw: spectrum_router: Replay MACVLANs when RIF is
made")

mlxsw_sp_rif_vid() has been unused since 2023's
commit a5b52692e693 ("mlxsw: spectrum_switchdev: Manage RIFs on PVID
change")

Remove them.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Link: https://patch.msgid.link/20250203190141.204951-1-linux@treblig.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>