lib: sbi: Allow specifying mode in sbi_hart_pmp_check_addr() API

We extend sbi_hart_pmp_check_addr() API so that users can specify
privilege mode of the address for checking PMP access permissions.

To achieve this, we end-up converting "unsigned long *size" parameter
to "unsigned long *log2len" for pmp_get() implementation so that we
can deal with regions of "1UL << __riscv_xlen" size in a special case
in sbi_hart_pmp_check_addr() implementation.

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