ASoC: OMAP: Remove obsolete Makefile line

Support for omap2evm was removed in v3.0. But only one of its two
lines in this Makefile was removed. Remove the second line too.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Acked-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>