net: stmmac: dwmac-loongson: Add new GMAC's PCI device ID support

net: stmmac: dwmac-loongson: Add new GMAC's PCI device ID support

Add a new GMAC's PCI device ID (0x7a23) support which is used in
Loongson-2K3000/Loongson-3B6000M. The new GMAC device use external PHY,
so it reuses loongson_gmac_data() as the old GMAC device (0x7a03), and
the new GMAC device still doesn't support flow control now.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Yanteng Si <si.yanteng@linux.dev>
Tested-by: Henry Chen <chenx97@aosc.io>
Tested-by: Biao Dong <dongbiao@loongson.cn>
Signed-off-by: Baoqi Zhang <zhangbaoqi@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Link: https://patch.msgid.link/20250424072209.3134762-4-chenhuacai@loongson.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>