openbsc: Fix the non-confirming SDP file

There must be a session name inside the SDP file, build a newer
version of OpenBSC to fix that.
diff --git a/recipes-osmocom/openbsc/openbsc_git.bb b/recipes-osmocom/openbsc/openbsc_git.bb
index 944867e..ba8bd0b 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 = "619b014d3aacea1b33b70432af01e80eb2252af0"
+SRCREV = "b1edf7b64f6c05932c83b4d31b1127f2a833601e"
 SRC_URI += "git://git.osmocom.org/openbsc.git;protocol=git \
     file://upgrade-mncc-version.patch"