ARM: ARTPEC-6: add select MFD_SYSCON to MACH_ARTPEC6

Since the ARTPEC-6 machine port already uses syscon,
MACH_ARTPEC6 should select MFD_SYSCON.
Signed-off-by: NNiklas Cassel <niklas.cassel@axis.com>
Signed-off-by: NJesper Nilsson <jespern@axis.com>

arch/arm/mach-artpec/Kconfig

@@ -14,6 +14,7 @@ config MACH_ARTPEC6
 	select HAVE_ARM_ARCH_TIMER
 	select HAVE_ARM_SCU
 	select HAVE_ARM_TWD if SMP
+	select MFD_SYSCON
 	help
 	  Support for Axis ARTPEC-6 ARM Cortex A9 Platform