libosmocore: Code is not in master so don't force SHA validation

The 0.9.0 release is in a different branch (+patches) and it is
easier to not write the branch name here.
diff --git a/recipes-osmocom/libosmocore/libosmocore_git.bb b/recipes-osmocom/libosmocore/libosmocore_git.bb
index e8db2bc..9101886 100644
--- a/recipes-osmocom/libosmocore/libosmocore_git.bb
+++ b/recipes-osmocom/libosmocore/libosmocore_git.bb
@@ -2,7 +2,7 @@
 
 S = "${WORKDIR}/git"
 SRCREV = "70fcbda6dd733a503e9a046e01986d8bfc2e2bb2"
-SRC_URI = "git://git.osmocom.org/libosmocore.git;protocol=git"
+SRC_URI = "git://git.osmocom.org/libosmocore.git;protocol=git;nobranch=1"
 PV = "0.9.0+gitr${SRCPV}"
 PR = "r0"