platform: andes/ae350: Remove enabling cache from an350_final_init

The boot-time cache operations have been handled by U-boot SPL, so we
can drop duplicate code.

Signed-off-by: Yu Chien Peter Lin <peterlin@andestech.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
Reviewed-by: Anup Patel <anup@brainfault.org>