config: update LEDE

- ath9k: add stability fixes for long standing hang issues (FS#13, #34, #373, #383)
  TP-Link TL-WR1043ND stable WiFi again
- Add back the commit "ath9k: Add airtime fairness scheduler"

config.mk

@@ -3,5 +3,5 @@ SHELL:=$(shell which bash)
 TARGET=ar71xx-generic
 PACKAGES_LIST_DEFAULT=default backbone
 LEDE_SRC=https://git.lede-project.org/source.git
-LEDE_COMMIT=f6de4a5025c758e05e53eb12f477a6dd27e4c42e
+LEDE_COMMIT=dfe77be01fb16178efc43350c431f998a3b65ff1
 MAKE_ARGS=