libfmq: Make dupeDesc const am: df1cb877b5

Original change: https://android-review.googlesource.com/c/platform/system/libfmq/+/3174401

Change-Id: I06b7c35c454e44a856ee152e0c1074701b3216f9
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>