staging: vboxvideo: Do not return -ENOSYS

New instances of ENOSYS are errors. ENOSYS should be used for nonexistent
syscalls only. Use ENODEV instead as there should not be any other
driver for a virtual device that might share buffers with vboxvideo.

In vbox_prime.c, replace all occurrences of -ENOSYS with -ENODEV to fix
checkpatch.pl warning:

WARNING: ENOSYS means 'invalid syscall nr' and nothing else
Signed-off-by: Debleena Sen <idebleenasen@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vboxvideo/vbox_prime.c

@@ -16,7 +16,7 @@
 int vbox_gem_prime_pin(struct drm_gem_object *obj)
 {
 	WARN_ONCE(1, "not implemented");
-	return -ENOSYS;
+	return -ENODEV;
 }
 
 void vbox_gem_prime_unpin(struct drm_gem_object *obj)
@@ -27,7 +27,7 @@ void vbox_gem_prime_unpin(struct drm_gem_object *obj)
 struct sg_table *vbox_gem_prime_get_sg_table(struct drm_gem_object *obj)
 {
 	WARN_ONCE(1, "not implemented");
-	return ERR_PTR(-ENOSYS);
+	return ERR_PTR(-ENODEV);
 }
 
 struct drm_gem_object *vbox_gem_prime_import_sg_table(
@@ -35,13 +35,13 @@ struct drm_gem_object *vbox_gem_prime_import_sg_table(
 	struct sg_table *table)
 {
 	WARN_ONCE(1, "not implemented");
-	return ERR_PTR(-ENOSYS);
+	return ERR_PTR(-ENODEV);
 }
 
 void *vbox_gem_prime_vmap(struct drm_gem_object *obj)
 {
 	WARN_ONCE(1, "not implemented");
-	return ERR_PTR(-ENOSYS);
+	return ERR_PTR(-ENODEV);
 }
 
 void vbox_gem_prime_vunmap(struct drm_gem_object *obj, void *vaddr)
@@ -52,5 +52,5 @@ void vbox_gem_prime_vunmap(struct drm_gem_object *obj, void *vaddr)
 int vbox_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *area)
 {
 	WARN_ONCE(1, "not implemented");
-	return -ENOSYS;
+	return -ENODEV;
 }