drm/i915/irq: Remove duplicated irq_enabled variable

Let's kill this legacy iand almost unused rq_enabled version
in favor of the real one that is checked at
intel_irqs_enabled().

The commit 'ac1723c16b66 ("drm/i915: Track IRQ state
in local device state")' shows that this was a legacy
DRM level irq_enabled information that got removed.

But the driver one already existed under a different
name.

Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240912172539.418957-1-rodrigo.vivi@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/i915_drv.h

@@ -343,8 +343,6 @@ struct drm_i915_private {
 
 	struct intel_pxp *pxp;
 
-	bool irq_enabled;
-
 	struct i915_pmu pmu;
 
 	/* The TTM device structure. */

drivers/gpu/drm/i915/i915_irq.c

@@ -1406,14 +1406,12 @@ int intel_irq_install(struct drm_i915_private *dev_priv)
 	 */
 	dev_priv->runtime_pm.irqs_enabled = true;
 
-	dev_priv->irq_enabled = true;
-
 	intel_irq_reset(dev_priv);
 
 	ret = request_irq(irq, intel_irq_handler(dev_priv),
 			  IRQF_SHARED, DRIVER_NAME, dev_priv);
 	if (ret < 0) {
-		dev_priv->irq_enabled = false;
+		dev_priv->runtime_pm.irqs_enabled = false;
 		return ret;
 	}
 
@@ -1439,11 +1437,9 @@ void intel_irq_uninstall(struct drm_i915_private *dev_priv)
 	 * intel_display_driver_remove() calling us out of sequence.
 	 * Would be nice if it didn't do that...
 	 */
-	if (!dev_priv->irq_enabled)
+	if (!dev_priv->runtime_pm.irqs_enabled)
 		return;
 
-	dev_priv->irq_enabled = false;
-
 	intel_irq_reset(dev_priv);
 
 	free_irq(irq, dev_priv);