FP5: Convert WiFi firmware symlink to install_symlink target

The last bit that was preventing building hermetic images.

Change-Id: I75bb7de4593a7992f6015317cf97e088beeba0cb
diff --git a/device.mk b/device.mk
index 2d67e73..39960e8 100644
--- a/device.mk
+++ b/device.mk
@@ -467,6 +467,10 @@
     frameworks/native/data/etc/android.hardware.wifi.xml:$(TARGET_COPY_OUT_VENDOR)/etc/permissions/android.hardware.wifi.xml \
     frameworks/native/data/etc/android.software.ipsec_tunnels.xml:$(TARGET_COPY_OUT_VENDOR)/etc/permissions/android.software.ipsec_tunnels.xml
 
+# WiFi firmware symlink
+PRODUCT_PACKAGES += \
+    firmware_WCNSS_qcom_cfg.ini_symlink
+
 # WiFi Display
 PRODUCT_PACKAGES += \
     android.media.audio.common.types-V2-cpp \