zenfone8: Remove duplicate include device.mk PRODUCT_MAKEFILES

Already include into omni_(device).mk

Fix: error: Product name must be unique, "device" used by device/asus/rog2/device.mk device/asus/zenfone6/device.mk

Change-Id: I8af8fd2ced5a55cb126f30cc4f5b4895ec114408
1 file changed