netdev-genl: Dump napi_defer_hard_irqs

Support dumping defer_hard_irqs for a NAPI ID.

Signed-off-by: Joe Damato <jdamato@fastly.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Link: https://patch.msgid.link/20241011184527.16393-3-jdamato@fastly.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/netdev.yaml

@@ -248,6 +248,13 @@ attribute-sets:
              threaded mode. If NAPI is not in threaded mode (i.e. uses normal
              softirq context), the attribute will be absent.
         type: u32
+      -
+        name: defer-hard-irqs
+        doc: The number of consecutive empty polls before IRQ deferral ends
+             and hardware IRQs are re-enabled.
+        type: u32
+        checks:
+          max: s32-max
   -
     name: queue
     attributes:
@@ -636,6 +643,7 @@ operations:
             - ifindex
             - irq
             - pid
+            - defer-hard-irqs
       dump:
         request:
           attributes: