android: binder: support for file-descriptor arrays.

This patch introduces a new binder_fd_array object,
that allows us to support one or more file descriptors
embedded in a buffer that is scatter-gathered.

Change-Id: I647a53cf0d905c7be0dfd9333806982def68dd74
Signed-off-by: Martijn Coenen <maco@google.com>
Git-commit: 74b2c7a5
Git-repo: https://android.googlesource.com/kernel/common


Signed-off-by: Swetha Chikkaboraiah <schikk@codeaurora.org>