drm: Avoid circular dependencies for CONFIG_FB

When cleaning up other drm config dependencies, it is too easy to create
larger problems. Instead, mark CONFIG_FB as a "depends":

drivers/gpu/drm/Kconfig:74:error: recursive dependency detected!

Suggested-by: Arnd Bergmann <arnd@kernel.org>
Link: https://lore.kernel.org/lkml/CAK8P3a3jUQs6c5tESSNMbqfuymewj9FhqRizyHcfOXf8Rgy-nA@mail.gmail.com/
Signed-off-by: Kees Cook <keescook@chromium.org>
[danvet: Rebase, the symbol has changed.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210602215252.695994-2-keescook@chromium.org

drivers/gpu/drm/Kconfig

@@ -95,8 +95,8 @@ config DRM_DEBUG_DP_MST_TOPOLOGY_REFS
 config DRM_FBDEV_EMULATION
 	bool "Enable legacy fbdev support for your modesetting driver"
 	depends on DRM
+	depends on FB
 	select DRM_KMS_HELPER
-	select FB
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA
 	select FB_CFB_IMAGEBLIT