ANDROID: GKI: locking/rwsem: add vendor field to struct rw_semaphore

For ABI compatibility, we are adding a vendor field to support the
config CONFIG_RWSEM_PRIO_AWARE.

Bug: 151792119
Bug: 148872640
Signed-off-by: Maria Yu <aiquny@codeaurora.org>
Signed-off-by: Biao long <blong@codeaurora.org>
[willmcvicker: Only cherry-picked the ABI diff]
(cherry picked from commit c4b6927b)
Signed-off-by: Will McVicker <willmcvicker@google.com>
Change-Id: I3f289e2992af340b56c2df532ffeb418abf3da79