net: Clarify dev_weight documentation for LRO and GRO_HW.

Reported-by: NMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: NMichael Chan <michael.chan@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/sysctl/net.txt

@@ -95,7 +95,9 @@ dev_weight
 --------------
 
 The maximum number of packets that kernel can handle on a NAPI interrupt,
-it's a Per-CPU variable.
+it's a Per-CPU variable. For drivers that support LRO or GRO_HW, a hardware
+aggregated packet is counted as one packet in this context.
+
 Default: 64
 
 dev_weight_rx_bias