dmclock: pick up fix to address FTBFS with GCC-9

Signed-off-by: Kefu Chai <kchai@redhat.com>

diff --git a/src/dmclock b/src/dmclock
index 5c82208802340fe240032f16604b0f9961247849..dd48b2110091e9db2d53a7c8e06d906abb907dbd 160000 (submodule)
--- a/src/dmclock
+++ b/src/dmclock
@@ -1 +1 @@
-Subproject commit 5c82208802340fe240032f16604b0f9961247849
+Subproject commit dd48b2110091e9db2d53a7c8e06d906abb907dbd