Add a generic locking API for situations where multiple user-space processes and/or kernel drivers need to cooordinate access to a shared resource such as a graphics buffer. Change-Id: Ic0dedbad74b970d7bd1a6624a845b5b1b9847443 Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>