This patch adds SiFive UART driver. The driver is 100% DM driver
and it determines input clock using clk framework.
Signed-off-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
