mlxsw: Switch to napi_gro_receive()

Benefit from the recent conversion of the driver to NAPI and enable GRO
support through the use of napi_gro_receive(). Pass the NAPI pointer
from the bus driver (mlxsw_pci) to the switch driver (mlxsw_spectrum)
through the skb control block where various packet metadata is already
encoded.

The main motivation is to improve forwarding performance through the use
of GRO fraglist [1]. In my testing, when the forwarding data path is
simple (routing between two ports) there is not much difference in
forwarding performance between GRO disabled and GRO enabled with
fraglist.

The improvement becomes more noticeable as the data path becomes more
complex since it is traversed less times with GRO enabled. For example,
with 10 ingress and 10 egress flower filters with different priorities
on the two ports between which routing is performed, there is an
improvement of about 140% in forwarded bandwidth.

[1] https://lore.kernel.org/netdev/20200125102645.4782-1-steffen.klassert@secunet.com/

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Link: https://patch.msgid.link/21258fe55f608ccf1ee2783a5a4534220af28903.1734354812.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>