lib: sbi: Configure PMP based on domain memory regions

The PMP configuration on each HART should be only based on the memory
regions of the assigned domain because each domain includes a memory
region to protect the underlying firmware.

This patch updates the sbi_hart_pmp_configure() function accordingly.

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