platform: andes/ae350: Cosmetic fixes in plicsw.c

- %s/CLINT/PLICSW
- replace '.' with a space
- add a space around * in plicsw_cold_ipi_init()

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>