sm8450-common: Decommonize mod_device property

Change-Id: Id3de1f7eb9fd392dad15e419dc253421c7fa18c0

properties/system.prop

@@ -45,6 +45,3 @@ ro.hardware.wlan.chip=qca6490
 ro.hardware.wlan.dbs=2
 ro.hardware.wlan.mimo=1
 ro.hardware.wlan.vendor=qcom
-
-# Xiaomi
-ro.product.mod_device=cupid_global