drm/aperture: Fix missing unlock on error in devm_aperture_acquire()

Add the missing unlock before return from function devm_aperture_acquire()
in the error handling case.

Signed-off-by: Zou Wei <zou_wei@huawei.com>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reported-by: Hulk Robot <hulkci@huawei.com>
Fixes: 730e7992 ("drm/aperture: Add infrastructure for aperture ownership")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Maxime Ripard <maxime@cerno.tech>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Link: https://patchwork.freedesktop.org/patch/msgid/1620895564-52367-1-git-send-email-zou_wei@huawei.com