igc: Change IGC_MIN to allow set rx/tx value between 64 and 80

Change the minimum value of RX/TX descriptors to 64 to enable setting the rx/tx
value between 64 and 80. All igc devices can use as low as 64 descriptors.
This change will unify igc with other drivers.
Based on commit 7b1be19 ("e1000e: lower ring minimum size to 64")

Fixes: 0507ef8 ("igc: Add transmit and receive fastpath and interrupt handlers")
Signed-off-by: Olga Zaborska <olga.zaborska@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

Author: ozaborska

drivers/net/ethernet/intel/igc/igc.h

@@ -379,11 +379,11 @@ static inline u32 igc_rss_type(const union igc_adv_rx_desc *rx_desc)
 /* TX/RX descriptor defines */
 #define IGC_DEFAULT_TXD		256
 #define IGC_DEFAULT_TX_WORK	128
-#define IGC_MIN_TXD		80
+#define IGC_MIN_TXD		64
 #define IGC_MAX_TXD		4096
 
 #define IGC_DEFAULT_RXD		256
-#define IGC_MIN_RXD		80
+#define IGC_MIN_RXD		64
 #define IGC_MAX_RXD		4096
 
 /* Supported Rx Buffer Sizes */