drm/msm: change gem->vmap() to get/put

Before we can add vmap shrinking, we really need to know which vmap'ings
are currently being used.  So switch to get/put interface.  Stubbed put
fxns for now.

Signed-off-by: Rob Clark <robdclark@gmail.com>
diff --git a/drivers/gpu/drm/msm/msm_drv.h b/drivers/gpu/drm/msm/msm_drv.h
index 4755894..ecf0b3b 100644
--- a/drivers/gpu/drm/msm/msm_drv.h
+++ b/drivers/gpu/drm/msm/msm_drv.h
@@ -200,8 +200,10 @@
 		struct dma_buf_attachment *attach, struct sg_table *sg);
 int msm_gem_prime_pin(struct drm_gem_object *obj);
 void msm_gem_prime_unpin(struct drm_gem_object *obj);
-void *msm_gem_vaddr_locked(struct drm_gem_object *obj);
-void *msm_gem_vaddr(struct drm_gem_object *obj);
+void *msm_gem_get_vaddr_locked(struct drm_gem_object *obj);
+void *msm_gem_get_vaddr(struct drm_gem_object *obj);
+void msm_gem_put_vaddr_locked(struct drm_gem_object *obj);
+void msm_gem_put_vaddr(struct drm_gem_object *obj);
 int msm_gem_madvise(struct drm_gem_object *obj, unsigned madv);
 void msm_gem_purge(struct drm_gem_object *obj);
 int msm_gem_sync_object(struct drm_gem_object *obj,