drm/meson: Uninstall IRQ handler

meson_drv_unbind() doesn't unregister the IRQ handler, which can lead to
use-after-free if the IRQ fires after unbind:

[   64.656876] Unable to handle kernel paging request at virtual address ffff000011706dbc
...
[   64.662001] pc : meson_irq+0x18/0x30 [meson_drm]

I'm assuming that a similar problem could happen on the error path of
bind(), so uninstall the IRQ handler there as well.

Fixes: bbbe775e ("drm: Add support for Amlogic Meson Graphic Controller")
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190322152657.13752-2-jean-philippe.brucker@arm.com

drivers/gpu/drm/meson/meson_drv.c

@@ -337,12 +337,14 @@ static int meson_drv_bind_master(struct device *dev, bool has_components)
 
 	ret = drm_dev_register(drm, 0);
 	if (ret)
-		goto free_drm;
+		goto uninstall_irq;
 
 	drm_fbdev_generic_setup(drm, 32);
 
 	return 0;
 
+uninstall_irq:
+	drm_irq_uninstall(drm);
 free_drm:
 	drm_dev_put(drm);
 
@@ -367,6 +369,7 @@ static void meson_drv_unbind(struct device *dev)
 	}
 
 	drm_dev_unregister(drm);
+	drm_irq_uninstall(drm);
 	drm_kms_helper_poll_fini(drm);
 	drm_mode_config_cleanup(drm);
 	drm_dev_put(drm);