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_gem_prime.c b/drivers/gpu/drm/msm/msm_gem_prime.c
index 6b90890..60bb290 100644
--- a/drivers/gpu/drm/msm/msm_gem_prime.c
+++ b/drivers/gpu/drm/msm/msm_gem_prime.c
@@ -33,12 +33,12 @@
 
 void *msm_gem_prime_vmap(struct drm_gem_object *obj)
 {
-	return msm_gem_vaddr(obj);
+	return msm_gem_get_vaddr(obj);
 }
 
 void msm_gem_prime_vunmap(struct drm_gem_object *obj, void *vaddr)
 {
-	/* TODO msm_gem_vunmap() */
+	msm_gem_put_vaddr(obj);
 }
 
 int msm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)