spi: bcm2835: switch to use modern name

Change legacy name master/slave to modern name host/target.

No functional changed.
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Link: https://lore.kernel.org/r/20230728093221.3312026-6-yangyingliang@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>