Switch to use modern name function spi_alloc_host().

No functional changed.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20230823033003.3407403-15-yangyingliang@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>