aosp_trout_arm64.mk: Pick up BOARD_VENDOR_RAMDISK_KERNEL_MODULES_DIR cmdline Linux kernel modules in the dir will be used to populate vendor_boot ramdisk. Bug: 225304945 Test: Set the variable and build. Check that modules propagated to the vendor ramdisk Change-Id: Ia0805c7ebeeedbdf75d5e1120bb3721a74674e2c