RISC-V: Add AIA related CSR defines

The RISC-V AIA specification improves handling per-HART local interrupts
in a backward compatible manner. This patch adds defines for new RISC-V
AIA CSRs.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>