lib: Add possible hart status values

SBI HSM extension defines possible hart status values in the
specification.

Define all possible status values. Add a helper function to
convert hart state to status because hart states are internal
to OpenSBI only and may not match the status values defined in
the specification.

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