sifive_u: Connect the SiFive PWM device

Connect the SiFive PWM device and expose it via the device tree.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Message-id: 22f98648b4e012f78529a56f5ca60b0b27852a4d.1631159656.git.alistair.francis@wdc.com
4 files changed