drm/xe: don't build debugfs files when CONFIG_DEBUG_FS=n

drm/xe: don't build debugfs files when CONFIG_DEBUG_FS=n

If we unconditionally build the debugfs files, we'll get both the static
inline stubs from the headers and the real functions for
CONFIG_DEBUG_FS=n. Avoid building the debugfs files with that config.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Closes: https://lore.kernel.org/r/152521f9-119f-4c61-b467-3e91f4aecb1a@infradead.org
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240124090515.3363901-1-jani.nikula@intel.com