gpu: drm: drm_vm: Adding new typedef vm_fault_t

Use new return type vm_fault_t for fault handler. For
now, this is just documenting that the function returns
a VM_FAULT value rather than an errno. Once all instances
are converted, vm_fault_t will become a distinct type.

commit 1c8f422059ae ("mm: change return type to vm_fault_t")

Signed-off-by: Souptick Joarder <[e-mail]>
Reviewed-by: Matthew Wilcox <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/20180510134203.GA25166@jordon-HP-15-Notebook-PC

drivers/gpu/drm/drm_vm.c

···
  * map, get the page, increment the use count and return it.
  */
 #if IS_ENABLED(CONFIG_AGP)
-static int drm_vm_fault(struct vm_fault *vmf)
+static vm_fault_t drm_vm_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	struct drm_file *priv = vma->vm_file->private_data;
···
 	return VM_FAULT_SIGBUS;	/* Disallow mremap */
 }
 #else
-static int drm_vm_fault(struct vm_fault *vmf)
+static vm_fault_t drm_vm_fault(struct vm_fault *vmf)
 {
 	return VM_FAULT_SIGBUS;
 }
···
  * Get the mapping, find the real physical page to map, get the page, and
  * return it.
  */
-static int drm_vm_shm_fault(struct vm_fault *vmf)
+static vm_fault_t drm_vm_shm_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	struct drm_local_map *map = vma->vm_private_data;
···
  *
  * Determine the page number from the page offset and get it from drm_device_dma::pagelist.
  */
-static int drm_vm_dma_fault(struct vm_fault *vmf)
+static vm_fault_t drm_vm_dma_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	struct drm_file *priv = vma->vm_file->private_data;
···
  *
  * Determine the map offset from the page offset and get it from drm_sg_mem::pagelist.
  */
-static int drm_vm_sg_fault(struct vm_fault *vmf)
+static vm_fault_t drm_vm_sg_fault(struct vm_fault *vmf)
 {
 	struct vm_area_struct *vma = vmf->vma;
 	struct drm_local_map *map = vma->vm_private_data;