spi: dw-mmio: keep old name same as documentation

The documentation has not use the new name(host/target),
so keep the comment words same as documentation used.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20230816093938.1274806-1-yangyingliang@huawei.com


Signed-off-by: Mark Brown <broonie@kernel.org>