spi: xtensa-xtfpga: Switch to use devm_spi_alloc_master()

Switch to use devm_spi_alloc_master() to simpify error path.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Tested-by: Max Filippov <jcmvbkbc@gmail.com>
Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Link: https://lore.kernel.org/r/20220920114448.2681053-1-yangyingliang@huawei.com


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