qca_spi: Introduce QCASPI_RX_MAX_FRAMES

Currently qca_spi reserves enough space for 4 complete Ethernet over SPI
frames in the receive buffer. Unfortunately this is hidden under a magic
number. So replace it with a more self explaining define.
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qualcomm/qca_spi.c

@@ -829,7 +829,7 @@ qcaspi_netdev_init(struct net_device *dev)
 	qca->burst_len = qcaspi_burst_len;
 	qca->spi_thread = NULL;
 	qca->buffer_size = (dev->mtu + VLAN_ETH_HLEN + QCAFRM_HEADER_LEN +
-		QCAFRM_FOOTER_LEN + 4) * 4;
+		QCAFRM_FOOTER_LEN + 4) * QCASPI_RX_MAX_FRAMES;
 
 	memset(&qca->stats, 0, sizeof(struct qcaspi_stats));
 

drivers/net/ethernet/qualcomm/qca_spi.h

@@ -41,6 +41,7 @@
 
 #define QCASPI_TX_RING_MAX_LEN 10
 #define QCASPI_TX_RING_MIN_LEN 2
+#define QCASPI_RX_MAX_FRAMES 4
 
 /* sync related constants */
 #define QCASPI_SYNC_UNKNOWN 0