net: stmmac: dwmac-loongson: Move queue number init to common function

Currently, the tx and rx queue number initialization is duplicated in
loongson_gmac_data() and loongson_gnet_data(), so move it to the common
function loongson_default_data().

This is a preparation for later patches.

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>
Signed-off-by: David S. Miller <davem@davemloft.net>