spi: Fix controller unregister order harder

Commit c7e41e1c sought to backport upstream commit 84855678add8 to
the 4.9-stable tree but erroneously inserted a line at the wrong place.
Fix it.

Fixes: c7e41e1c ("spi: Fix controller unregister order")
Reported-by: yangerkun <yangerkun@huawei.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>