openbsc: Upgrade for AudioCodes workaround

Mostly SGSN fixes, one OML correctness fix. The reason for the
upgrade is the audio codes work around we added.
diff --git a/recipes-osmocom/openbsc/openbsc_git.bb b/recipes-osmocom/openbsc/openbsc_git.bb
index 17e897a..944867e 100644
--- a/recipes-osmocom/openbsc/openbsc_git.bb
+++ b/recipes-osmocom/openbsc/openbsc_git.bb
@@ -3,7 +3,7 @@
 PV = "0.13.0+gitr${SRCPV}"
 PR = "${INC_PR}.6"
 
-SRCREV = "db64f2e45adf7ac95070361f5b7ec76a44e084fb"
+SRCREV = "619b014d3aacea1b33b70432af01e80eb2252af0"
 SRC_URI += "git://git.osmocom.org/openbsc.git;protocol=git \
     file://upgrade-mncc-version.patch"