update libopencm3

diff --git a/libopencm3 b/libopencm3
index 5bc6bc430a768a2e7392af4f4c93f306a0a654ba..2faa482669cb5984a87cf2b17bdbf4c8b83c23a0 160000 (submodule)
--- a/libopencm3
+++ b/libopencm3
@@ -1 +1 @@
-Subproject commit 5bc6bc430a768a2e7392af4f4c93f306a0a654ba
+Subproject commit 2faa482669cb5984a87cf2b17bdbf4c8b83c23a0