drm: define drm_compat_ioctl NULL on CONFIG_COMPAT=n and reduce #ifdefs

If we define drm_compat_ioctl NULL on CONFIG_COMPAT=n, we don't have to
check for the config everywhere.

Reviewed-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1478014844-27454-1-git-send-email-jani.nikula@intel.com

drivers/gpu/drm/hisilicon/kirin/kirin_drm_drv.c

@@ -152,9 +152,7 @@ static const struct file_operations kirin_drm_fops = {
 	.open		= drm_open,
 	.release	= drm_release,
 	.unlocked_ioctl	= drm_ioctl,
-#ifdef CONFIG_COMPAT
 	.compat_ioctl	= drm_compat_ioctl,
-#endif
 	.poll		= drm_poll,
 	.read		= drm_read,
 	.llseek		= no_llseek,