mlxsw: reg: Add priority field for PTCEV2 register

This is going to be needed for Spectrum-2 C-TCAM implementation.

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