mlxsw: Remove old parsing depth infrastructure

The previous patches added new API to handle parsing depth and converted
the existing code to use it.

Remove the old infrastructure which is not needed anymore.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>