ufdt: use size_t for iteration in ufdt_apply_multioverlay am: 76c3a18e69 am: 5a3a19cc0b

Original change: https://android-review.googlesource.com/c/platform/system/libufdt/+/3368290

Change-Id: Ia737200c0b9659e7325bbb2ed1ecff5fbef31b1b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>