libutils: Make LightFlattenablePod safe for unaligned ptr

`buffer` may not be correctly aligned here. Assignment assumes correct
alignment and so then blows up on arm32.

Bug: b/37920153
Test: build, boot device
Change-Id: I23ef7c7f1d1511fd912b9485bba955db59e33832
diff --git a/libutils/include/utils/Flattenable.h b/libutils/include/utils/Flattenable.h
index 22b811a..070c710 100644
--- a/libutils/include/utils/Flattenable.h
+++ b/libutils/include/utils/Flattenable.h
@@ -189,11 +189,11 @@
     }
     inline status_t flatten(void* buffer, size_t size) const {
         if (size < sizeof(T)) return NO_MEMORY;
-        *reinterpret_cast<T*>(buffer) = *static_cast<T const*>(this);
+        memcpy(buffer, static_cast<T const*>(this), sizeof(T));
         return NO_ERROR;
     }
     inline status_t unflatten(void const* buffer, size_t) {
-        *static_cast<T*>(this) = *reinterpret_cast<T const*>(buffer);
+        memcpy(static_cast<T*>(this), buffer, sizeof(T));
         return NO_ERROR;
     }
 };