[][MAC80211][core][Update nf_flow_offload_tuple panic issue]

[Description]
Add down_write()/up_write() to mtk_eth_setup_tc_block().

If without this patch, kernel might panic in the nf_flow_offload_tuple()
in network interface down/up test.

[Release-log]
N/A


Change-Id: Ic0d5b4fede5a943a79f6e180686838c215d381cf
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6604264
Build: srv_hbgsm110
2 files changed