lib: sbi: Configure PMP late in coldboot and warmboot path

We factor-out PMP configuration from sbi_hart_init() as a separate
sbi_hart_pmp_configure() function and do the PMP configuration very
late in coldboot and warmboot path just before platform_final_init().

Eventually, this enable us to configure PMP totally based on OpenSBI
domain where OpenSBI domains can be parsed from device-tree in any of
the platform operations except platform_final_init().

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>