drm/i810: Refer to `PREEMPTION' in comment

The dependency has been changed from `PREEMPT' to `PREEMPTION'. Reflect
this change in the comment.

Use `PREEMPTION' in the comment.

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20191015191821.11479-29-bigeasy@linutronix.de

drivers/gpu/drm/Kconfig

@@ -404,7 +404,7 @@ config DRM_R128
 
 config DRM_I810
 	tristate "Intel I810"
-	# !PREEMPT because of missing ioctl locking
+	# !PREEMPTION because of missing ioctl locking
 	depends on DRM && AGP && AGP_INTEL && (!PREEMPTION || BROKEN)
 	help
 	  Choose this option if you have an Intel I810 graphics card.  If M is