Revert "device property: Constify device child node APIs"

This reverts commit 0ba045ab which is
commit 7952cd2b upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I4aba9d5a6b2b8467e5ed1a0cde4f87018ecf256a
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>