ARM: hisi: select HAVE_ARM_SCU only for SMP

The SCU code does not build unless we are compiling
an SMP kernel. This does the same as every other
platform with an SCU.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>