[PATCH v7 15/22] riscv: Clean up IPI initialization code

[Rick Chen]

> The previous IPI code initialized the device whenever the first call was
> made to a riscv_*_ipi function. This made it difficult to determine when
> the IPI device was initialized. This patch introduces a new function
> riscv_init_ipi. It is called once during arch_cpu_init_dm. Before this
> point, no riscv_*_ipi functions should be called.
>
> Signed-off-by: Sean Anderson <seanga2 at gmail.com>

Reviewed-by: Rick Chen <rick at andestech.com>