spi_controller_is_slave() and spi_slave_abort() are all replaced,
so they can be removed.

No functional changed.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://patch.msgid.link/20240910022618.1397-8-yangyingliang@huaweicloud.comSigned-off-by: Mark Brown <broonie@kernel.org>