Don't pass --setup_as_rootfs_from_kernel when using a super partition.

When the system partition is a dynamic partition, the device will be
using an initial ramdisk and should not have a root device specified on
the kernel command-line.

Bug: 115939310
Test: device boots when BOARD_SUPER_PARTITION_PARTITION_LIST contains
      super and AVB is enabled.

Change-Id: I5c4b2304bf1ab6a59443c43c354845bf8a3949f0