gma500: fix an incorrect NULL check on list iterator

stable inclusion
from stable-v5.10.121
commit 591c3481b13fa6d5d03819e90539fa442c6ed2d2
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6CQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=591c3481b13fa6d5d03819e90539fa442c6ed2d2



--------------------------------

commit bdef417d upstream.

The bug is here:
	return crtc;

The list iterator value 'crtc' will *always* be set and non-NULL by
list_for_each_entry(), so it is incorrect to assume that the iterator
value will be NULL if the list is empty or no element is found.

To fix the bug, return 'crtc' when found, otherwise return NULL.

Cc: stable@vger.kernel.org
fixes: 89c78134 ("gma500: Add Poulsbo support")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
Signed-off-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220327052028.2013-1-xiam0nd.tong@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>