The hartid can be a 64bit value on RV64 platforms.

Add support for 64bit hartid in riscv_of_processor_hartid() and
update its callers.
Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20220527051743.2829940-5-sunilvl@ventanamicro.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>