platform: andes: Change all occurrences of andes45 to andes

To make the framework suit all Andes CPUs, change all occurrences of
andes45 to andes.

In addition, we fix some coding style problems and remove an unused
macro in andes.h.

Signed-off-by: Ben Zong-You Xie <ben717@andestech.com>
Reviewed-by: Anup Patel <anup@brainfault.org>