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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Robert Richter <robert.richter@amd.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>