drm/i915: get rid of intel_plane_restore in intel_crtc_page_flip

drm/i915: get rid of intel_plane_restore in intel_crtc_page_flip

Use a full atomic call instead. intel_crtc_page_flip will still
have to live until async updates are allowed.

This doesn't seem to be a regression from the convert to atomic,
part 3 patch. During GPU reset it fixes the following warning:

 ------------[ cut here ]------------
WARNING: CPU: 0 PID: 752 at drivers/gpu/drm/drm_crtc.c:5337 drm_mode_page_flip_ioctl+0x27b/0x360()
Modules linked in: i915
CPU: 0 PID: 752 Comm: Xorg Not tainted 4.1.0-rc7-patser+ #4090
Hardware name: NUC5i7RYB, BIOS RYBDWi35.86A.0246.2015.0309.1355 03/09/2015
 ffffffff81c90866 ffff8800d87c3ca8 ffffffff817f7d87 0000000080000001
 0000000000000000 ffff8800d87c3ce8 ffffffff81084955 ffff880000000000
 ffff8800d87c3dc0 ffff8800d93d1208 0000000000000000 ffff8800b7d1f3e0
Call Trace:
 [<ffffffff817f7d87>] dump_stack+0x4f/0x7b
 [<ffffffff81084955>] warn_slowpath_common+0x85/0xc0
 [<ffffffff81084a35>] warn_slowpath_null+0x15/0x20
 [<ffffffff8146dffb>] drm_mode_page_flip_ioctl+0x27b/0x360
 [<ffffffff8145ccb0>] drm_ioctl+0x1a0/0x6a0
 [<ffffffff810b3b41>] ? get_parent_ip+0x11/0x50
 [<ffffffff812e5540>] ? avc_has_perm+0x20/0x280
 [<ffffffff810b3b41>] ? get_parent_ip+0x11/0x50
 [<ffffffff811ea0f8>] do_vfs_ioctl+0x2f8/0x530
 [<ffffffff811f6001>] ? expand_files+0x261/0x270
 [<ffffffff812e7c16>] ? selinux_file_ioctl+0x56/0x100
 [<ffffffff811ea3b1>] SyS_ioctl+0x81/0xa0
 [<ffffffff81801b97>] system_call_fastpath+0x12/0x6f
---[ end trace 9ce834560085bd64 ]---

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>