sh: fix build failure for J2 cpu with SMP disabled

The sh asm/smp.h defines a fallback hard_smp_processor_id macro for
the !SMP case, but linux/smp.h never includes asm/smp.h in the !SMP
case.
Signed-off-by: NRich Felker <dalias@libc.org>

arch/sh/kernel/cpu/sh2/probe.c

@@ -43,7 +43,11 @@ void __ref cpu_probe(void)
 #endif
 
 #if defined(CONFIG_CPU_J2)
+#if defined(CONFIG_SMP)
 	unsigned cpu = hard_smp_processor_id();
+#else
+	unsigned cpu = 0;
+#endif
 	if (cpu == 0) of_scan_flat_dt(scan_cache, NULL);
 	if (j2_ccr_base) __raw_writel(0x80000303, j2_ccr_base + 4*cpu);
 	if (cpu != 0) return;