drm: Select DRM_KMS_HELPER from DRM_DEBUG_DP_MST_TOPOLOGY_REFS

Using "depends on" and "select" for the same Kconfig symbol is known to
cause circular dependencies (cmp. "Kconfig recursive dependency
limitations" in Documentation/kbuild/kconfig-language.rst.
DRM drivers are selecting drm helpers so do the same for
DRM_DEBUG_DP_MST_TOPOLOGY_REFS.
Fixes following circular dependency reported on x86 for the downstream
Asahi Linux tree:

error: recursive dependency detected!
  symbol DRM_KMS_HELPER is selected by DRM_GEM_SHMEM_HELPER
  symbol DRM_GEM_SHMEM_HELPER is selected by RUST_DRM_GEM_SHMEM_HELPER
  symbol RUST_DRM_GEM_SHMEM_HELPER is selected by DRM_ASAHI
  symbol DRM_ASAHI depends on RUST
  symbol RUST depends on CALL_PADDING
  symbol CALL_PADDING depends on OBJTOOL
  symbol OBJTOOL is selected by STACK_VALIDATION
  symbol STACK_VALIDATION depends on UNWINDER_FRAME_POINTER
  symbol UNWINDER_FRAME_POINTER is part of choice block at arch/x86/Kconfig.debug:224
  symbol <choice> unknown is visible depending on UNWINDER_GUESS
  symbol UNWINDER_GUESS prompt is visible depending on STACKDEPOT
  symbol STACKDEPOT is selected by DRM_DEBUG_DP_MST_TOPOLOGY_REFS
  symbol DRM_DEBUG_DP_MST_TOPOLOGY_REFS depends on DRM_KMS_HELPER

Fixes: 12a280c ("drm/dp_mst: Add topology ref history tracking for debugging")
Cc: stable@vger.kernel.org
Signed-off-by: Janne Grunau <j@jannau.net>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20250304-drm_debug_dp_mst_topo_kconfig-v1-1-e16fd152f258@jannau.net
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>

Author: jannau

drivers/gpu/drm/Kconfig

@@ -188,7 +188,7 @@ config DRM_DEBUG_DP_MST_TOPOLOGY_REFS
         bool "Enable refcount backtrace history in the DP MST helpers"
 	depends on STACKTRACE_SUPPORT
         select STACKDEPOT
-        depends on DRM_KMS_HELPER
+        select DRM_KMS_HELPER
         depends on DEBUG_KERNEL
         depends on EXPERT
         help