put libusb1-dev into osmocom SDK

this is helpful for SDK-based development of applications accessing
USB from userspace (like simtrace).
diff --git a/recipes-osmocom/packagegroup/packagegroup-sdk-osmo.inc b/recipes-osmocom/packagegroup/packagegroup-sdk-osmo.inc
index 8a52016..7e3b709 100644
--- a/recipes-osmocom/packagegroup/packagegroup-sdk-osmo.inc
+++ b/recipes-osmocom/packagegroup/packagegroup-sdk-osmo.inc
@@ -1,4 +1,5 @@
 SDK-OSMO = " \
+    libusb1-dev \
     libtalloc-dev \
     libosmocore-dev \
     libosmo-sccp-staticdev \