gralloc: In lock use writer info from allocation time

lock() can be called from a CpuConsumer with only the READ_OFTEN flag
so relying only on that makes gralloc assume there are no non cpu
writers.

Store the writer information during allocation in private flags of
handle and refer to those during lock()

Change-Id: Ifbf25ebc74dbf4e422a2fdec52ec000cd75e549b
4 files changed