drm/msm: Extract out syncobj helpers

We'll be re-using these for the VM_BIND ioctl.

Also, rename a few things in the uapi header to reflect that syncobj use
is not specific to the submit ioctl.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
Tested-by: Antonino Maniscalco <antomani103@gmail.com>
Reviewed-by: Antonino Maniscalco <antomani103@gmail.com>
Patchwork: https://patchwork.freedesktop.org/patch/661512/