opkg: bump to version 2017-07-11

Commits since last 2017-05-03

    52fc006 pkg_alternatives: pass if the desired symlink already exists
    c668fce opkg: add --no-check-certificate argument

Signed-off-by: Yousong Zhou <yszhou4tech@gmail.com>

package/system/opkg/Makefile

@@ -16,9 +16,9 @@ PKG_FLAGS:=essential
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://git.lede-project.org/project/opkg-lede.git
-PKG_SOURCE_DATE:=2017-05-03
-PKG_SOURCE_VERSION:=04e279eb1c0e37e324d955969780cfec272442b9
-PKG_MIRROR_HASH:=f5cbfc6461760e35ac6f352cd9d9d6d668a27457fd66d862d9e6379bf6595dea
+PKG_SOURCE_DATE:=2017-07-11
+PKG_SOURCE_VERSION:=52fc0069b50b9be89ae3b525b98741123461dd0a
+PKG_MIRROR_HASH:=f7b0ea689b6e3f1cf680514bd59b13d9cd33c8255056b49af85e512554f97ccf
 
 PKG_LICENSE:=GPL-2.0
 PKG_LICENSE_FILES:=COPYING