ARM: SIRF: select SMP_ON_UP only on SMP builds

Like all other platforms, we can only select SMP_ON_UP if SMP
is also enabled.

warning: (SOC_IMX31 && SOC_IMX35 && ARCH_MARCO) selects
 SMP_ON_UP which has unmet direct dependencies (SMP && !XIP_KERNEL)

Cc: Barry Song <baohua.song@csr.com>
Signed-off-by: NArnd Bergmann <arnd@arndb.de>

arch/arm/mach-prima2/Kconfig

@@ -17,7 +17,7 @@ config ARCH_MARCO
 	select ARM_GIC
 	select CPU_V7
 	select HAVE_SMP
-	select SMP_ON_UP
+	select SMP_ON_UP if SMP
 	help
           Support for CSR SiRFSoC ARM Cortex A9 Platform