Remove ndk_platform backend. Use the ndk backend. am: e11f34b4fb am: 090df9b4f4 am: d0d09e8613 am: 394a47a318

Original change: https://android-review.googlesource.com/c/platform/system/keymaster/+/1779386

Change-Id: I330dd9836a48cf48e03718dc339a439a5e03cd4b