mlxsw: reg.h: Namespace IP2ME registers

This renames IP2ME-specific registers reg_ralue_v and
reg_ralue_tunnel_ptr to reg_ralue_ip2me_*.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>