e1000e: lower ring minimum size to 64

The lower limit of 80 descriptors in the ring is only valid for
one older 8254x chipset. All e1000e devices can use as low as
64 descriptors.
Signed-off-by: NAuke Kok <auke-jan.h.kok@intel.com>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>

drivers/net/e1000e/e1000.h

@@ -64,11 +64,11 @@ struct e1000_info;
 /* Tx/Rx descriptor defines */
 #define E1000_DEFAULT_TXD		256
 #define E1000_MAX_TXD			4096
-#define E1000_MIN_TXD			80
+#define E1000_MIN_TXD			64
 
 #define E1000_DEFAULT_RXD		256
 #define E1000_MAX_RXD			4096
-#define E1000_MIN_RXD			80
+#define E1000_MIN_RXD			64
 
 #define E1000_MIN_ITR_USECS		10 /* 100000 irq/sec */
 #define E1000_MAX_ITR_USECS		10000 /* 100    irq/sec */