mlxsw: spectrum_router: Increase parsing depth for IPv6 decapsulation

The Spectrum ASIC has a configurable limit on how deep into the packet
it parses. By default, the limit is 96 bytes.

For IP-in-IP packets, with IPv6 outer and inner headers, the default
parsing depth is not enough and without increasing it such packets cannot
be properly decapsulated.

Use the existing API to set parsing depth, call it once for each
decapsulation entry when it is created/destroyed.
There is no need to protect the code with new mutex because 'router->lock'
is already taken in these code paths.

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