drm/sun4i: dw-hdmi: fix error return code in sun8i_dw_hdmi_bind()

Fix to return a negative error code from the error handling case instead
of 0 in function sun8i_dw_hdmi_bind().

Fixes: b7c7436a

 ("drm/sun4i: Implement A83T HDMI driver")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Xiongfeng Wang <wangxiongfeng2@huawei.com>
Reviewed-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Link: https://patchwork.freedesktop.org/patch/msgid/1605488969-5211-1-git-send-email-wangxiongfeng2@huawei.com