Do not select BACKLIGHT_CLASS_DEVICE from FB_BACKLIGHT. The latter
only controls backlight support within fbdev core code and data
structures.

Make fbdev drivers depend on BACKLIGHT_CLASS_DEVICE and let users
select it explicitly. Fixes warnings about recursive dependencies,
such as

error: recursive dependency detected!
	symbol BACKLIGHT_CLASS_DEVICE is selected by FB_BACKLIGHT
	symbol FB_BACKLIGHT is selected by FB_SH_MOBILE_LCDC
	symbol FB_SH_MOBILE_LCDC depends on FB_DEVICE
	symbol FB_DEVICE depends on FB_CORE
	symbol FB_CORE is selected by DRM_GEM_DMA_HELPER
	symbol DRM_GEM_DMA_HELPER is selected by DRM_PANEL_ILITEK_ILI9341
	symbol DRM_PANEL_ILITEK_ILI9341 depends on BACKLIGHT_CLASS_DEVICE

BACKLIGHT_CLASS_DEVICE is user-selectable, so making drivers adapt to
it is the correct approach in any case. For most drivers, backlight
support is also configurable separately.

v3:
- Select BACKLIGHT_CLASS_DEVICE in PowerMac defconfigs (Christophe)
- Fix PMAC_BACKLIGHT module dependency corner cases (Christophe)
v2:
- s/BACKLIGHT_DEVICE_CLASS/BACKLIGHT_CLASS_DEVICE (Helge)
- Fix fbdev driver-dependency corner case (Arnd)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
  arch/powerpc/configs/pmac32_defconfig |  1 +
  arch/powerpc/configs/ppc6xx_defconfig |  1 +
  drivers/auxdisplay/Kconfig            |  2 +-
  drivers/macintosh/Kconfig             |  1 +
  drivers/staging/fbtft/Kconfig         |  1 +
  drivers/video/fbdev/Kconfig           | 18 +++++++++++++-----
  drivers/video/fbdev/core/Kconfig      |  3 +--
  7 files changed, 19 insertions(+), 8 deletions(-)

...

diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
index de035071fedb..55c6686f091e 100644
--- a/drivers/video/fbdev/Kconfig
+++ b/drivers/video/fbdev/Kconfig

@@ -649,6 +649,7 @@ config FB_S1D13XXX
  config FB_ATMEL
  	tristate "AT91 LCD Controller support"
  	depends on FB && OF && HAVE_CLK && HAS_IOMEM
+	depends on BACKLIGHT_CLASS_DEVICE
  	depends on HAVE_FB_ATMEL || COMPILE_TEST
  	select FB_BACKLIGHT
  	select FB_IOMEM_HELPERS

@@ -660,7 +661,6 @@ config FB_ATMEL
  config FB_NVIDIA
  	tristate "nVidia Framebuffer Support"
  	depends on FB && PCI
-	select FB_BACKLIGHT if FB_NVIDIA_BACKLIGHT
  	select FB_CFB_FILLRECT
  	select FB_CFB_COPYAREA
  	select FB_CFB_IMAGEBLIT

@@ -700,6 +700,8 @@ config FB_NVIDIA_DEBUG
  config FB_NVIDIA_BACKLIGHT
  	bool "Support for backlight control"
  	depends on FB_NVIDIA
+	depends on BACKLIGHT_CLASS_DEVICE=y || BACKLIGHT_CLASS_DEVICE=FB_NVIDIA