DRM: more fixes for heap base mapping

Heap base for the same heap could be mapped to different values
after they go across binder to CryptoHal. So we can't use heapbase
to index the heaps.

Since each ACodec instance allocates all its shared memory buffers
from the same memory dealer, we let CryptoHal assign a sequence
number to the ACodec when it calls setHeap. In subsequent calls
to CryptoHal::decrypt, reference the heap by the seq num, and ignore
the heap base address.

Bug: 36479980
Bug: 36209723
Bug: 36660223

Test: the above bugs don't repro

Change-Id: I2f519a689a5891447385d1bf9d6e668bb3b4dbe2