spi: dw-mmio: Do not add acpi modalias when CONFIG_ACPI is not enabled

Reduce unnecessary static memory allocation when CONFIG_ACPI is not enabled.

Signed-off-by: Jay Fang <f.fangjian@huawei.com>
Link: https://lore.kernel.org/r/1588991392-24219-1-git-send-email-f.fangjian@huawei.com
Signed-off-by: Mark Brown <broonie@kernel.org>