drm/hisilicon/hibmc: Remove variable 'priv' from hibmc_unload()

The variable 'priv' got introduced in commit 39a364a1
("drm/hisilicon/hibmc: Convert to Linux IRQ interfaces") by accident.
It's unused; remove it. Fixes a compiler warning.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 39a364a1 ("drm/hisilicon/hibmc: Convert to Linux IRQ interfaces")
Reviewed-by: Tian Tao <tiantao6@hisilicon.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reported-by: Dave Airlie <airlied@gmail.com>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Tian Tao <tiantao6@hisilicon.com>
Cc: Maxime Ripard <maxime@cerno.tech>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210721131704.10306-1-tzimmermann@suse.de