drm: pass the irq explicitly to drm_irq_install

Unfortunately this requires a drm-wide change, and I didn't see a sane
way around that. Luckily it's fairly simple, we just need to inline
the respective get_irq implementation from either drm_pci.c or
drm_platform.c.

With that we can now also remove drm_dev_to_irq from drm_irq.c.

Reviewed-by: Thierry Reding <treding@nvidia.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Documentation/DocBook/drm.tmpl

@@ -341,14 +341,6 @@ char *date;</synopsis>
         </para>
         <sect4>
           <title>Managed IRQ Registration</title>
-          <para>
-            Both the <function>drm_irq_install</function> and
-	    <function>drm_irq_uninstall</function> functions get the device IRQ by
-	    calling <function>drm_dev_to_irq</function>. This inline function will
-	    call a bus-specific operation to retrieve the IRQ number. For platform
-	    devices, <function>platform_get_irq</function>(..., 0) is used to
-	    retrieve the IRQ number.
-          </para>
           <para>
             <function>drm_irq_install</function> starts by calling the
             <methodname>irq_preinstall</methodname> driver operation. The operation
@@ -356,7 +348,7 @@ char *date;</synopsis>
             clearing all pending interrupt flags or disabling the interrupt.
           </para>
           <para>
-            The IRQ will then be requested by a call to
+            The passed-in IRQ will then be requested by a call to
             <function>request_irq</function>. If the DRIVER_IRQ_SHARED driver
             feature flag is set, a shared (IRQF_SHARED) IRQ handler will be
             requested.