Fix L3 HLS decryption

A recent change to avoid returning decrypted data
over binder assumed that in-place decryption was
safe. That isn't true for the L3 HLS case. This
change eliminates the assumption that in-place
decryption is safe while still returning the
decrypted data via shared memory, instead of
copying it over binder.

bug: 31657897
Change-Id: I7e480a25d2f9b08e54a4844ecdf19ba3c8af79c2