Extend sifive_u machine to allow passing custom DTB using "-dtb"
command-line parameter. This will help users pass modified DTB
or Linux SiFive DTB to sifive_u machine.
Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20201022053225.2596110-1-anup.patel@wdc.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>