net: dsa: mt7530: Add MT7621 TRGMII mode support

This patch add support TRGMII mode for MT7621 internal MT7530 switch.
MT7621 TRGMII has only one fix speed mode of 1200MBit.

Also adding support for mt7530 25MHz and 40MHz crystal clocksource.
Values are based on Banana Pi R2 bsp [1].

Don't change MT7623 registers on a MT7621 device.

[1] https://github.com/BPI-SINOVOIP/BPI-R2-bsp/blob/master/linux-mt/drivers/net/ethernet/mediatek/gsw_mt7623.c#L769

Signed-off-by: René van Dorst <opensource@vdorst.com>
Tested-by: Frank Wunderlich <frank-w@public-files.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mt7530.h

@@ -244,6 +244,10 @@ enum mt7530_vlan_port_attr {
 
 /* Register for hw trap status */
 #define MT7530_HWTRAP			0x7800
+#define  HWTRAP_XTAL_MASK		(BIT(10) | BIT(9))
+#define  HWTRAP_XTAL_25MHZ		(BIT(10) | BIT(9))
+#define  HWTRAP_XTAL_40MHZ		(BIT(10))
+#define  HWTRAP_XTAL_20MHZ		(BIT(9))
 
 /* Register for hw trap modification */
 #define MT7530_MHWTRAP			0x7804