frameworks/av: convert LOCAL_MODULE_PATH to LOCAL_MODULE_RELATIVE_PATH

LOCAL_MODULE_PATH doesn't work for multiarch builds, replace it
with LOCAL_MODULE_RELATIVE_PATH.

Change-Id: I4e4ceec61d026bbe74ba604554c06104bde42e5e
diff --git a/media/libeffects/proxy/Android.mk b/media/libeffects/proxy/Android.mk
index 01b3be1..d6d6c1e 100644
--- a/media/libeffects/proxy/Android.mk
+++ b/media/libeffects/proxy/Android.mk
@@ -15,7 +15,7 @@
 LOCAL_PATH:= $(call my-dir)
 include $(CLEAR_VARS)
 LOCAL_MODULE:= libeffectproxy
-LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/soundfx
+LOCAL_MODULE_RELATIVE_PATH := soundfx
 LOCAL_MODULE_TAGS := optional