drm/i915: s/pm._irqs_disabled/pm.irqs_enabled/

Double negations just parse harder. Also this allows us to ditch some
init code since clearing to 0 dtrt. Also ditch the assignment in
intel_pm_setup, that's not redundant since we do the assignement now
while setting up interrupts.

While at it do engage in a bit of OCD and wrap up the few lines of
setup/teardown code into little helper functions: intel_irq_fini for
cleanup and intel_irq_init_hw for hw setup.

v2: Use _install/_uninstall for the new wrapper function names as
Paulo suggested.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 5dbd5c9..b4c4f6f 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1424,7 +1424,7 @@
  */
 struct i915_runtime_pm {
 	bool suspended;
-	bool _irqs_disabled;
+	bool irqs_enabled;
 };
 
 enum intel_pipe_crc_source {
@@ -2311,6 +2311,8 @@
 							int new_delay);
 extern void intel_irq_init(struct drm_device *dev);
 extern void intel_hpd_init(struct drm_device *dev);
+int intel_irq_install(struct drm_i915_private *dev_priv);
+void intel_irq_uninstall(struct drm_i915_private *dev_priv);
 
 extern void intel_uncore_sanitize(struct drm_device *dev);
 extern void intel_uncore_early_sanitize(struct drm_device *dev,