opkg: update to latest Git head

cb66403 libopkg: check for file size mismatches

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

package/system/opkg/Makefile

@@ -14,9 +14,9 @@ PKG_FLAGS:=essential
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://git.openwrt.org/project/opkg-lede.git
-PKG_SOURCE_DATE:=2019-01-18
-PKG_SOURCE_VERSION:=7708a01a084872bbe4c46f36d2da021fdeb10862
-PKG_MIRROR_HASH:=117148ece22e64654264afd869606ef5507edd3dc965ffe000c6b1b1074b3f4a
+PKG_SOURCE_DATE:=2019-01-31
+PKG_SOURCE_VERSION:=cb6640381808dd629cfa58a21ceaf12e91a82e68
+PKG_MIRROR_HASH:=5a3feaea086818494b93fceae8c8e3182e2cefccfb5cb8eccb275d9730496288
 
 PKG_LICENSE:=GPL-2.0
 PKG_LICENSE_FILES:=COPYING