modules: update OpenWrt

f8cc68670fcf mediatek: fix parallel build issues in image build code
1086408b17fa mtd: improve check for TRX header being already fixed
5dca299fabc4 mtd: support bad blocks within the mtd_fixtrx()
5889cf70e99f kmod-sched-cake: bump to 20180716
393ee8d0b28a qos-scripts: fix uci callback handling
c9c0fc28a9c4 base-files: fix UCI config parsing and callback handling
aee917a5a28d apm821xx: fix usb-otg on 4.14
3539430b3daa odhcp6c: add noserverunicast config option for broken DHCPv6 servers
6363377c477f odhcp6c: update to latest git HEAD
ce8cab388aab odhcp6c: user string option support
dc52b7b104aa ipq40xx: add get_status_led to diag.sh
7fc7128b086a OpenWrt v18.06.0-rc2: revert to branch defaults
4de335bdbed6 OpenWrt v18.06.0-rc2: adjust config defaults
e4d0ee5af5a0 uhttpd: update to latest Git head

modules

@@ -2,7 +2,7 @@ GLUON_FEEDS='packages routing luci gluon'
 
 OPENWRT_REPO=https://git.openwrt.org/openwrt/openwrt.git
 OPENWRT_BRANCH=openwrt-18.06
-OPENWRT_COMMIT=a7b2764879dbcf7c6b1d5463158c4e51ca993974
+OPENWRT_COMMIT=f8cc68670fcf2e6912ead308240ce1af4652b8c3
 
 PACKAGES_PACKAGES_REPO=https://github.com/openwrt/packages.git
 PACKAGES_PACKAGES_BRANCH=openwrt-18.06