riscv: smp: Add 64bit hartid support on RV64

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

Modify the hartid parameter in riscv_hartid_to_cpuid() as
unsigned long so that it can hold 64bit value on RV64 platforms.

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20220527051743.2829940-4-sunilvl@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>