get rid of separate multipage fault-in primitives

* the only remaining callers of "short" fault-ins are just as happy with generic
variants (both in lib/iov_iter.c); switch them to multipage variants, kill the
"short" ones
* rename the multipage variants to now available plain ones.
* get rid of compat macro defining iov_iter_fault_in_multipage_readable by
expanding it in its only user.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index a77ce99..ccf56c6 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -675,7 +675,7 @@
 
 	mutex_unlock(&dev->struct_mutex);
 	if (likely(!i915.prefault_disable)) {
-		ret = fault_in_multipages_writeable(user_data, remain);
+		ret = fault_in_pages_writeable(user_data, remain);
 		if (ret) {
 			mutex_lock(&dev->struct_mutex);
 			goto out_unpin;
@@ -803,7 +803,7 @@
 		mutex_unlock(&dev->struct_mutex);
 
 		if (likely(!i915.prefault_disable) && !prefaulted) {
-			ret = fault_in_multipages_writeable(user_data, remain);
+			ret = fault_in_pages_writeable(user_data, remain);
 			/* Userspace is tricking us, but we've already clobbered
 			 * its pages with the prefault and promised to write the
 			 * data up to the first fault. Hence ignore any errors
@@ -1267,7 +1267,7 @@
 		return -EFAULT;
 
 	if (likely(!i915.prefault_disable)) {
-		ret = fault_in_multipages_readable(u64_to_user_ptr(args->data_ptr),
+		ret = fault_in_pages_readable(u64_to_user_ptr(args->data_ptr),
 						   args->size);
 		if (ret)
 			return -EFAULT;