gpu/drm: Ingenic: Fix opaque pointer casted to wrong type

gpu/drm: Ingenic: Fix opaque pointer casted to wrong type

The opaque pointer passed to the IRQ handler is a pointer to the
drm_device, not a pointer to our ingenic_drm structure.

It still worked, because our ingenic_drm structure contains the
drm_device as its first field, so the pointer received had the same
value, but this was not semantically correct.

Cc: stable@vger.kernel.org # v5.3
Fixes: c7eedec560a4 ("DRM: Add KMS driver for the Ingenic JZ47xx SoCs")
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20200516215057.392609-5-paul@crapouillou.net
Acked-by: Sam Ravnborg <sam@ravnborg.org>