drm: Include <linux/backlight.h> where needed

Include <linux/backlight.h> in source files that need it. Some of
DRM's source code gets the backlight header via drm_crtc_helper.h
and <linux/fb.h>, which can leed to unnecessary recompilation. If
possible, do not include drm_crtc_helper.h any longer.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Christian König <christian.koenig@amd.com> # amd
Acked-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20230111130206.29974-2-tzimmermann@suse.de

drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c

@@ -24,6 +24,7 @@
 
 #include <linux/pci.h>
 #include <linux/acpi.h>
+#include <linux/backlight.h>
 #include <linux/slab.h>
 #include <linux/power_supply.h>
 #include <linux/pm_runtime.h>
@@ -31,7 +32,6 @@
 #include <acpi/video.h>
 #include <acpi/actbl.h>
 
-#include <drm/drm_crtc_helper.h>
 #include "amdgpu.h"
 #include "amdgpu_pm.h"
 #include "amdgpu_display.h"

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -67,6 +67,7 @@
 #include "ivsrcid/ivsrcid_vislands30.h"
 
 #include "i2caux_interface.h"
+#include <linux/backlight.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/types.h>

drivers/gpu/drm/gma500/backlight.c

@@ -7,6 +7,8 @@
  * Authors: Eric Knopp
  */
 
+#include <linux/backlight.h>
+
 #include <acpi/video.h>
 
 #include "psb_drv.h"

drivers/gpu/drm/radeon/radeon_acpi.c

@@ -22,6 +22,7 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/backlight.h>
 #include <linux/pci.h>
 #include <linux/pm_runtime.h>
 #include <linux/power_supply.h>
@@ -30,7 +31,6 @@
 #include <acpi/acpi_bus.h>
 #include <acpi/video.h>
 
-#include <drm/drm_crtc_helper.h>
 #include <drm/drm_probe_helper.h>
 
 #include "atom.h"