drm/nv50: rework PGPIO IRQ handling and hotplug detection

Allows callers to install their own handlers for when a GPIO line
changes state (such as for hotplug detect).

This also fixes a bug where we weren't acknowledging the GPIO IRQ
until after the bottom half had run, causing a severe IRQ storm
in some cases.

Reviewed-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nv50_display.h

@@ -36,7 +36,6 @@
 #include "nv50_evo.h"
 
 void nv50_display_irq_handler_bh(struct work_struct *work);
-void nv50_display_irq_hotplug_bh(struct work_struct *work);
 int nv50_display_early_init(struct drm_device *dev);
 void nv50_display_late_takedown(struct drm_device *dev);
 int nv50_display_create(struct drm_device *dev);