bnxt_en: Reduce default ring sizes.

The current default tx ring size of 512 causes an extra page to be
allocated for the tx ring with only 1 entry in it.  Reduce it to
511.  The default rx ring size is also reduced to 511 to use less
memory by default.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bnxt/bnxt.h

@@ -411,8 +411,8 @@ struct rx_tpa_end_cmp_ext {
 
 #define BNXT_NUM_TESTS(bp)	0
 
-#define BNXT_DEFAULT_RX_RING_SIZE	1023
-#define BNXT_DEFAULT_TX_RING_SIZE	512
+#define BNXT_DEFAULT_RX_RING_SIZE	511
+#define BNXT_DEFAULT_TX_RING_SIZE	511
 
 #define MAX_TPA		64