drm/i915: Drop struct_mutex from suspend state save/restore

struct_mutex provides no serialisation of the registers and data
structures being saved and restored across suspend/resume. It is
completely superfluous here.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191004134015.13204-19-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_suspend.c

@@ -66,8 +66,6 @@ int i915_save_state(struct drm_i915_private *dev_priv)
 	struct pci_dev *pdev = dev_priv->drm.pdev;
 	int i;
 
-	mutex_lock(&dev_priv->drm.struct_mutex);
-
 	i915_save_display(dev_priv);
 
 	if (IS_GEN(dev_priv, 4))
@@ -101,8 +99,6 @@ int i915_save_state(struct drm_i915_private *dev_priv)
 			dev_priv->regfile.saveSWF3[i] = I915_READ(SWF3(i));
 	}
 
-	mutex_unlock(&dev_priv->drm.struct_mutex);
-
 	return 0;
 }
 
@@ -111,8 +107,6 @@ int i915_restore_state(struct drm_i915_private *dev_priv)
 	struct pci_dev *pdev = dev_priv->drm.pdev;
 	int i;
 
-	mutex_lock(&dev_priv->drm.struct_mutex);
-
 	if (IS_GEN(dev_priv, 4))
 		pci_write_config_word(pdev, GCDGMBUS,
 				      dev_priv->regfile.saveGCDGMBUS);
@@ -146,8 +140,6 @@ int i915_restore_state(struct drm_i915_private *dev_priv)
 			I915_WRITE(SWF3(i), dev_priv->regfile.saveSWF3[i]);
 	}
 
-	mutex_unlock(&dev_priv->drm.struct_mutex);
-
 	intel_gmbus_reset(dev_priv);
 
 	return 0;