Merge branch 'mediatek-rx-path-enhancements'

Sean Wang says:

====================
net: ethernet: mediatek: add enhancements to RX path

Changes since v1:
- fix message typos and add coverletter

Changes since v2:
- split from the previous series for submitting add enhancements as
a series targeting 'net-next' and add indents before comments.

Changes since v3:
- merge the patch using PDMA RX path
- fixed the input of mtk_poll_rx is with the remaining budget

Changes since v4:
- save one wmb and register update when no packet is being handled
inside mtk_poll_rx call
- fixed incorrect return packet count from mtk_napi_rx
====================

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