lib: sbi: Remove redundant hartid parameter from sbi_hart_init()

The hartid parameter of sbi_hart_init() is not used anywhere in
sbi_hart_init() implementation so let's remove it.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>