ASoC: eliminate left-over from Raumfeld machine driver removal

Commit f84a6273 ("ASoC: pxa: remove raumfeld machine driver")
removed the Raumfeld ASoC machine driver but forgot to kill one line
in the Makefile.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: Mark Brown <broonie@kernel.org>