net: stmmac: Parse FIFO sizes from feature registers

New version of this core encode the FIFO sizes in one of the feature
registers. Use these sizes as default, but still allow device tree to
override them for backwards compatibility.

Reviewed-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac4.h

@@ -148,6 +148,8 @@ enum power_event {
 /* MAC HW features1 bitmap */
 #define GMAC_HW_FEAT_AVSEL		BIT(20)
 #define GMAC_HW_TSOEN			BIT(18)
+#define GMAC_HW_TXFIFOSIZE		GENMASK(10, 6)
+#define GMAC_HW_RXFIFOSIZE		GENMASK(4, 0)
 
 /* MAC HW features2 bitmap */
 #define GMAC_HW_FEAT_TXCHCNT		GENMASK(21, 18)