net: ethernet: mtk_eth_soc: increase MAX_DEVS to 3

This is a preliminary patch to add MT7988 SoC support since it runs 3
macs instead of 2.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://lore.kernel.org/r/3563e5fab367e7d79a7f1296fabaa5c20f202d7a.1690246066.git.daniel@makrotopia.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: LorenzoBianconi

drivers/net/ethernet/mediatek/mtk_eth_soc.h

@@ -1043,8 +1043,8 @@ struct mtk_soc_data {
 
 #define MTK_DMA_MONITOR_TIMEOUT		msecs_to_jiffies(1000)
 
-/* currently no SoC has more than 2 macs */
-#define MTK_MAX_DEVS			2
+/* currently no SoC has more than 3 macs */
+#define MTK_MAX_DEVS	3
 
 /* struct mtk_eth -	This is the main datasructure for holding the state
  *			of the driver