net: napi: Add napi_config

net: napi: Add napi_config

Add a persistent NAPI config area for NAPI configuration to the core.
Drivers opt-in to setting the persistent config for a NAPI by passing an
index when calling netif_napi_add_config.

napi_config is allocated in alloc_netdev_mqs, freed in free_netdev
(after the NAPIs are deleted).

Drivers which call netif_napi_add_config will have persistent per-NAPI
settings: NAPI IDs, gro_flush_timeout, and defer_hard_irq settings.

Per-NAPI settings are saved in napi_disable and restored in napi_enable.

Co-developed-by: Martin Karsten <mkarsten@uwaterloo.ca>
Signed-off-by: Martin Karsten <mkarsten@uwaterloo.ca>
Signed-off-by: Joe Damato <jdamato@fastly.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20241011184527.16393-6-jdamato@fastly.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>