Add near-ultrasound system properties for flounder/volantis.

Change-Id: I2d4bdb457cbfaf47d4b5ced40b506dbcbaa4475e
diff --git a/device.mk b/device.mk
index df24776..29f9d91 100644
--- a/device.mk
+++ b/device.mk
@@ -237,6 +237,11 @@
 PRODUCT_PROPERTY_OVERRIDES += \
     ro.audio.monitorRotation=true
 
+# Near-ultrasound support in the default audio and speaker paths.
+PRODUCT_PROPERTY_OVERRIDES += \
+    persist.audio.spkr.ultrasound=true \
+    persist.audio.mic.ultrasound=true
+
 # for sound trigger on DSP
 PRODUCT_PACKAGES += \
     sound_trigger.primary.flounder