e1000e: 82574/82583 performance improvement

Increasing the transmit fifo by 4K (by decreasing the receive fifo size
specified in .pba by the same amount) increases Tx performance.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Emil Tantilov <emil.s.tantilov@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/e1000e/82571.c

@@ -2005,7 +2005,7 @@ struct e1000_info e1000_82574_info = {
 				  | FLAG_HAS_AMT
 				  | FLAG_HAS_CTRLEXT_ON_LOAD,
 	.flags2			  = FLAG2_CHECK_PHY_HANG,
-	.pba			= 36,
+	.pba			= 32,
 	.max_hw_frame_size	= DEFAULT_JUMBO,
 	.get_variants		= e1000_get_variants_82571,
 	.mac_ops		= &e82571_mac_ops,
@@ -2022,7 +2022,7 @@ struct e1000_info e1000_82583_info = {
 				  | FLAG_HAS_SMART_POWER_DOWN
 				  | FLAG_HAS_AMT
 				  | FLAG_HAS_CTRLEXT_ON_LOAD,
-	.pba			= 36,
+	.pba			= 32,
 	.max_hw_frame_size	= ETH_FRAME_LEN + ETH_FCS_LEN,
 	.get_variants		= e1000_get_variants_82571,
 	.mac_ops		= &e82571_mac_ops,