Revert "drm/nouveau: add kconfig option to turn off nouveau legacy contexts. (v3)"

This reverts commit 1e07d637 which is
commit b30a43ac upstream.

Sven reports:
	Commit 1e07d637 ("drm/nouveau: add kconfig option to turn off nouveau
	legacy contexts. (v3)") has caused a build failure for me when I
	actually tried that option (CONFIG_NOUVEAU_LEGACY_CTX_SUPPORT=n):

	,----
	| Kernel: arch/x86/boot/bzImage is ready  (#1)
	|   Building modules, stage 2.
	|   MODPOST 290 modules
	| ERROR: "drm_legacy_mmap" [drivers/gpu/drm/nouveau/nouveau.ko] undefined!
	| scripts/Makefile.modpost:91: recipe for target '__modpost' failed
	`----

	Upstream does not have that problem, as commit bed2dd84 ("drm/ttm:
	Quick-test mmap offset in ttm_bo_mmap()") has removed the use of
	drm_legacy_mmap from nouveau_ttm.c.  Unfortunately that commit does not
	apply in 5.1.9.

The ensuing discussion proposed a number of one-off patches, but no
solid agreement was made, so just revert the commit for now to get
people's systems building again.
Reported-by: Sven Joachim <svenjoac@gmx.de>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Thomas Backlund <tmb@mageia.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/nouveau/Kconfig

@@ -17,20 +17,9 @@ config DRM_NOUVEAU
 	select INPUT if ACPI && X86
 	select THERMAL if ACPI && X86
 	select ACPI_VIDEO if ACPI && X86
-	help
-	  Choose this option for open-source NVIDIA support.
-
-config NOUVEAU_LEGACY_CTX_SUPPORT
-	bool "Nouveau legacy context support"
-	depends on DRM_NOUVEAU
 	select DRM_VM
-	default y
 	help
-	  There was a version of the nouveau DDX that relied on legacy
-	  ctx ioctls not erroring out. But that was back in time a long
-	  ways, so offer a way to disable it now. For uapi compat with
-	  old nouveau ddx this should be on by default, but modern distros
-	  should consider turning it off.
+	  Choose this option for open-source NVIDIA support.
 
 config NOUVEAU_PLATFORM_DRIVER
 	bool "Nouveau (NVIDIA) SoC GPUs"

drivers/gpu/drm/nouveau/nouveau_drm.c

@@ -1094,11 +1094,8 @@ nouveau_driver_fops = {
 static struct drm_driver
 driver_stub = {
 	.driver_features =
-		DRIVER_GEM | DRIVER_MODESET | DRIVER_PRIME | DRIVER_RENDER
-#if defined(CONFIG_NOUVEAU_LEGACY_CTX_SUPPORT)
-		| DRIVER_KMS_LEGACY_CONTEXT
-#endif
-		,
+		DRIVER_GEM | DRIVER_MODESET | DRIVER_PRIME | DRIVER_RENDER |
+		DRIVER_KMS_LEGACY_CONTEXT,
 
 	.open = nouveau_drm_open,
 	.postclose = nouveau_drm_postclose,