ASoC: Intel: fix ACPI probe regression with Atom DPCM driver

The commit 95f09801
"ASoC: Intel: Move apci find machine routines"

introduced a regression in ACPI probe of the DPCM driver.
Fix by conditionally compiling sst-acpi when the DPCM driver
is not selected

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>