drm/vkms: Create separate Kconfig file for VKMS

This aligns with most other DRM drivers and will allow
us to add new VKMS config options without polluting
the DRM Kconfig.

v3:
 - Change SPDX to GPL-2.0-only to match DRM KConfig
   SPDX (Simon)
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Simon Ser <contact@emersion.fr>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231108163647.106853-4-harry.wentland@amd.com

drivers/gpu/drm/Kconfig

@@ -287,19 +287,7 @@ config DRM_VGEM
 	  as used by Mesa's software renderer for enhanced performance.
 	  If M is selected the module will be called vgem.
 
-config DRM_VKMS
-	tristate "Virtual KMS (EXPERIMENTAL)"
-	depends on DRM && MMU
-	select DRM_KMS_HELPER
-	select DRM_GEM_SHMEM_HELPER
-	select CRC32
-	default n
-	help
-	  Virtual Kernel Mode-Setting (VKMS) is used for testing or for
-	  running GPU in a headless machines. Choose this option to get
-	  a VKMS.
-
-	  If M is selected the module will be called vkms.
+source "drivers/gpu/drm/vkms/Kconfig"
 
 source "drivers/gpu/drm/exynos/Kconfig"
 

drivers/gpu/drm/vkms/Kconfig

+# SPDX-License-Identifier: GPL-2.0-only
+
+config DRM_VKMS
+	tristate "Virtual KMS (EXPERIMENTAL)"
+	depends on DRM && MMU
+	select DRM_KMS_HELPER
+	select DRM_GEM_SHMEM_HELPER
+	select CRC32
+	default n
+	help
+	  Virtual Kernel Mode-Setting (VKMS) is used for testing or for
+	  running GPU in a headless machines. Choose this option to get
+	  a VKMS.
+
+	  If M is selected the module will be called vkms.