lib: sbi_hsm: Fix sbi_hsm_hart_start() for platform with hart hotplug

It possible that a platform supports hart hotplug (i.e. both hart_start
and hart_stop callbacks available) and all harts are start simultaneously
at platform boot-time. In this situation, the sbi_hsm_hart_start() will
call hsm_device_hart_start() for secondary harts at platform boot-time
which will fail because secondary harts were already started.

To fix above, we call hsm_device_hart_start() from sbi_hsm_hart_start()
only when entry_count is same as init_count for the secondary hart.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>