perf/x86/ibs: Fix undefined reference to `get_ibs_caps'

Fixing i386 allnoconfig built errors:

 arch/x86/built-in.o: In function `amd_pmu_hw_config':
 perf_event_amd.c:(.text+0xc3e1): undefined reference to `get_ibs_caps'
Reported-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NRobert Richter <robert.richter@amd.com>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

arch/x86/include/asm/perf_event.h

@@ -188,7 +188,11 @@ struct x86_pmu_capability {
 #define IBS_OP_MAX_CNT_EXT	0x007FFFFFULL	/* not a register bit mask */
 #define IBS_RIP_INVALID		(1ULL<<38)
 
+#ifdef CONFIG_X86_LOCAL_APIC
 extern u32 get_ibs_caps(void);
+#else
+static inline u32 get_ibs_caps(void) { return 0; }
+#endif
 
 #ifdef CONFIG_PERF_EVENTS
 extern void perf_events_lapic_init(void);