classpath: fix alsa-related build failure

Classpath requires sequencer support besides pcm support. Fixes:
http://autobuild.buildroot.org/results/2bd/2bd39ffa821bc02d64998bc9e8fe178d3741a1d8/



Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>