mpd: fix alsa dependencies

Alsa output support needs pcm and mixer support in alsa-lib.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/multimedia/mpd/Config.in

@@ -18,6 +18,8 @@ config BR2_PACKAGE_MPD_ALSA
 	bool "alsa"
 	default y
 	select BR2_PACKAGE_ALSA_LIB
+	select BR2_PACKAGE_ALSA_LIB_PCM
+	select BR2_PACKAGE_ALSA_LIB_MIXER
 	help
 	  Enable alsa output support.