Since we will not longer be modifying events in place, we don't need
to use an ashmem region for input. Simplified the code to instead
use a socket of type SOCK_SEQPACKET.
This is part of a series of changes to improve input system pipelining.
Bug: 5963420
Change-Id: I05909075ed8b61b93900913e44c6db84857340d8