drm/i915: Drop unused struct_mutex from drm_i915_private

The struct_mutex field in drm_i915_private is no longer used anywhere in
the driver. This patch removes it completely to clean up unused code and
avoid confusion.

Signed-off-by: Luiz Otavio Mello <luiz.mello@estudante.ufscar.br>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/20250908131518.36625-9-luiz.mello@estudante.ufscar.br
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Author: LuizOt31

drivers/gpu/drm/i915/i915_driver.c

@@ -235,7 +235,6 @@ static int i915_driver_early_probe(struct drm_i915_private *dev_priv)
 
 	intel_sbi_init(display);
 	vlv_iosf_sb_init(dev_priv);
-	mutex_init(&dev_priv->struct_mutex);
 	mutex_init(&dev_priv->sb_lock);
 
 	i915_memcpy_init_early(dev_priv);
@@ -294,7 +293,6 @@ static void i915_driver_late_release(struct drm_i915_private *dev_priv)
 	i915_workqueues_cleanup(dev_priv);
 
 	mutex_destroy(&dev_priv->sb_lock);
-	mutex_destroy(&dev_priv->struct_mutex);
 	vlv_iosf_sb_fini(dev_priv);
 	intel_sbi_fini(display);
 

drivers/gpu/drm/i915/i915_drv.h

@@ -223,14 +223,6 @@ struct drm_i915_private {
 
 	bool irqs_enabled;
 
-	/*
-	 * Currently, struct_mutex is only used by the i915 driver as a replacement
-	 * for BKL.
-	 *
-	 * For this reason, it is no longer part of struct drm_device.
-	 */
-	struct mutex struct_mutex;
-
 	/* LPT/WPT IOSF sideband protection */
 	struct mutex sbi_lock;