hw/display/virtio-gpu.c: use reset_bh class method

hw/display/virtio-gpu.c: use reset_bh class method

While the VirtioGPU type has a reset_bh field to specify a reset
callback, it's never used. virtio_gpu_reset() calls the general
virtio_gpu_reset_bh() function for all devices that inherit from
VirtioGPU.

While no devices override reset_bh at the moment, a device reset might
require special logic for implementations in the future.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Message-Id: <87fb4fa72ce5b341a6f957513a00dcb79fd5997f.1706626470.git.manos.pitsidianakis@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>