spi: Fix modalias for ACPI enumerated SPI devices

There is a minor fault about ACPI enumerated SPI devices with their modalias
attribute. Now modalias is set by device instance not by hardware ID.
For example "spi:INTABCD:00", "spi:INTABCD:01" etc.

This means each device instance gets different modalias which does match
with generated modules.alias. Currently this is not problem as matching can
happen also with "acpi:INTABCD" modalias.

Fix this by using ACPI hardware ID.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>