net: ena: change rx copybreak default to reduce kernel memory pressure

BugLink: http://bugs.launchpad.net/bugs/1798182

Improves socket memory utilization when receiving packets larger
than 128 bytes (the previous rx copybreak) and smaller than 256 bytes.
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 87731f0c linux-next)
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Acked-by: Khalid Elmously <khalid.elmously@canonical.com>
Acked-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

drivers/net/ethernet/amazon/ena/ena_netdev.h

@@ -78,7 +78,7 @@
 #define ENA_DEFAULT_RING_SIZE	(1024)
 
 #define ENA_TX_WAKEUP_THRESH		(MAX_SKB_FRAGS + 2)
-#define ENA_DEFAULT_RX_COPYBREAK	(128 - NET_IP_ALIGN)
+#define ENA_DEFAULT_RX_COPYBREAK	(256 - NET_IP_ALIGN)
 
 /* limit the buffer size to 600 bytes to handle MTU changes from very
  * small to very large, in which case the number of buffers per packet