ARM: hisi: fix kconfig warning on HAVE_ARM_TWD

Commit "ARM: hisi: don't select SMP" introduced a kconfig warning:
warning: (ARCH_HI3xxx) selects HAVE_ARM_TWD which has unmet direct dependencies (SMP)

Fix HAVE_ARM_TWD to depend on SMP.

Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Olof Johansson <olof@lixom.net>

arch/arm/mach-hisi/Kconfig

@@ -8,7 +8,7 @@ config ARCH_HI3xxx
 	select CLKSRC_OF
 	select GENERIC_CLOCKEVENTS
 	select HAVE_ARM_SCU
-	select HAVE_ARM_TWD
+	select HAVE_ARM_TWD if SMP
 	select HAVE_SMP
 	select PINCTRL
 	select PINCTRL_SINGLE