ARM: shmobile: don't call platform_can_secondary_boot on UP

For rcar-gen2, we build the SMP files even for UP configurations,
and that just broke:

arch/arm/mach-shmobile/built-in.o: In function `shmobile_smp_init_fallback_ops':
pm-rcar-gen2.c:(.init.text+0x40c): undefined reference to `platform_can_secondary_boot'

This adds an compile-time check before the call to platform_can_secondary_boot,
turning the function into an empty stub for UP configurations.

Signed-off-by: Arnd Bergmann <[e-mail]>
Fixes: c21af444eace ("ARM: shmobile: smp: Add function to prioritize DT SMP")
Acked-by: Geert Uytterhoeven <[e-mail]>
Signed-off-by: Olof Johansson <[e-mail]>

arch/arm/mach-shmobile/platsmp.c

···
 bool __init shmobile_smp_init_fallback_ops(void)
 {
 	/* fallback on PSCI/smp_ops if no other DT based method is detected */
+	if (!IS_ENABLED(CONFIG_SMP))
+		return false;
+
 	return platform_can_secondary_boot() ? true : false;
 }