modules: update openwrt

81388f74b5 scripts/download.pl: fix downloads with wget
b8cbca8ac8 scripts/download.pl: silence can't exec curl warning
340b138932 scripts: always check certificates
b5e39355e4 tools: remove xxd package
b531611f57 build: provide xxd -i with scripts/xxdi.pl
542447b93e scripts: xxdi.pl: add xxd -i compat mode
4c795af58b scripts: xxdi.pl: remove File::Slurp dependency
a352e30b8f scripts: add xxdi.pl
b3fa0241e2 mac80211: backport tx queueing bugfixes add a bug fix for a rare crash
94372ab6e4 bcm53xx: update NVMEM driver for NVRAM
cae4d089bc kernel: backport mtd dynamic partition patch