myri10ge: small rx_done refactoring

Avoid theoretical race condition regarding accessing dev->features
NETIF_F_LRO flag, which is illustrated below.

CPU1					CPU2

myri10ge_clean_rx_done():		myri10ge_set_flags():
					or
					myri10ge_set_rx_csum():

if (dev->features & NETIF_F_LRO)
        setup lro
					dev->features |= NETIF_F_LRO
					or
					dev->features &= ~NETIF_F_LRO;
if (dev->features & NETIF_F_LRO)
        flush lro

On the way reduce myri10ge_rx_done() number of arguments and calls by
moving mgp->small_bytes check into that function. That reduce code size

from:
   text	   data	    bss	    dec	    hex	filename
  36644	    248	    100	  36992	   9080	drivers/net/myri10ge/myri10ge.o

to:
   text	   data	    bss	    dec	    hex	filename
  36037	    247	    100	  36384	   8e20	drivers/net/myri10ge/myri10ge.o

on my i686 system, what should also make myri10ge_clean_rx_done()
being faster.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>