drm/xe: Make wedged_mode debugfs writable

The intent of this debugfs entry is to allow modification of wedging
behavior, either from IGT tests or during manual debug; it should be
marked as writable to properly reflect this.  In practice this hasn't
caused a problem because we always access wedged_mode as root, which
ignores file permissions, but it's still misleading to have the entry
incorrectly marked as RO.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Fixes: 6b8ef44c ("drm/xe: Introduce the wedged_mode debugfs")
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241002230620.1249258-2-matthew.d.roper@intel.com
(cherry picked from commit 93d93813422758f6c99289de446b19184019ef5a)
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

drivers/gpu/drm/xe/xe_debugfs.c

@@ -187,7 +187,7 @@ void xe_debugfs_register(struct xe_device *xe)
 	debugfs_create_file("forcewake_all", 0400, root, xe,
 			    &forcewake_all_fops);
 
-	debugfs_create_file("wedged_mode", 0400, root, xe,
+	debugfs_create_file("wedged_mode", 0600, root, xe,
 			    &wedged_mode_fops);
 
 	for (mem_type = XE_PL_VRAM0; mem_type <= XE_PL_VRAM1; ++mem_type) {