lib: sbi: Fix AIA feature detection

The AIA feature detection uses unnecessary goto which is not need
and AIA case in sbi_hart_feature_id2string() does not break. This
patch fixes both issues in AIA feature detection.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>