[][kernel][common][eth][Add SW path PPPQ and PPPQ toggle]

[Description]
Add SW path PPPQ and PPPQ toggle.

1.The min/max rate limit of QDMA TX queues will be set according to
the link speed of different ports when Ethernet cable is connected.
2.Ethernet driver will send packets to the mapped QDMA TX queue
according to the interface information to limit speed.
3.PPPQ toggle can be switched via the following command(default 0):
echo 0/1 > /sys/kernel/debug/mtketh/pppq_toggle

Without this patch, SW path bidirectional throughput unbalance
issue will occur.

[Release-log]
N/A


Change-Id: I9759e63159d6bc082f8a37b81a9330db78a3f47b
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/8596109
5 files changed