spi: amd: Use devm_platform_ioremap_resource() in amd_spi_probe

Simplify this function implementation by using a known wrapper function.

Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Link: https://lore.kernel.org/r/1605930231-19448-1-git-send-email-zhangqing@loongson.cn


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