package/mediastreamer: add optional dependency to speexdsp

Fixes
http://autobuild.buildroot.net/results/594/594ea96cd7b6726052268a3c0b094e00e7b8f12f/

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/mediastreamer/mediastreamer.mk

@@ -46,7 +46,7 @@ MEDIASTREAMER_CONF_OPTS += --disable-opus
 endif
 
 # portaudio backend needs speex as well
-ifeq ($(BR2_PACKAGE_PORTAUDIO)$(BR2_PACKAGE_SPEEX),yy)
+ifeq ($(BR2_PACKAGE_PORTAUDIO)$(BR2_PACKAGE_SPEEX)$(BR2_PACKAGE_SPEEXDSP),yyy)
 MEDIASTREAMER_CONF_OPTS += --enable-portaudio
 MEDIASTREAMER_DEPENDENCIES += portaudio speex
 else