x86/smp: fix non-SMP broken build due to redefinition of apic_id_is_primary_thread

The function has an inline "return false;" definition with CONFIG_SMP=n
but the "real" definition is also visible leading to "redefinition of
‘apic_id_is_primary_thread’" compiler error.

Guard it with #ifdef CONFIG_SMP
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Fixes: 6a4d2657 ("x86/smp: Provide topology_is_primary_thread()")
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/kernel/apic/apic.c

@@ -2193,6 +2193,7 @@ static int cpuid_to_apicid[] = {
 	[0 ... NR_CPUS - 1] = -1,
 };
 
+#ifdef CONFIG_SMP
 /**
  * apic_id_is_primary_thread - Check whether APIC ID belongs to a primary thread
  * @id:	APIC ID to check
@@ -2207,6 +2208,7 @@ bool apic_id_is_primary_thread(unsigned int apicid)
 	mask = (1U << (fls(smp_num_siblings) - 1)) - 1;
 	return !(apicid & mask);
 }
+#endif
 
 /*
  * Should use this API to allocate logical CPU IDs to keep nr_logical_cpuids