lib: utils/irqchip: Add APLIC initialization library

We add simple APLIC initialization library which is independent of
hardware description format (FDT or ACPI). This APLIC initialization
library can be used by custom OpenSBI platform support to setup
APLIC domains.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>