commit 
85bac32c4a52c592b857f2c360cc5ec93a097d70
    ring-buffer: only enable ring_buffer_swap_cpu when needed
broke oprofile (at least on s390, but likely on all platforms).
this patch lets oprofile select RING_BUFER_ALLOW_SWAP to make
ring_buffer_swap_cpu usable for oprofile.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
LKML-Reference: <
200909162156.49239.borntraeger@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Robert Richter <robert.richter@amd.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
        depends on TRACING_SUPPORT
        select TRACING
        select RING_BUFFER
+       select RING_BUFFER_ALLOW_SWAP
        help
          OProfile is a profiling system capable of profiling the
          whole system, include the kernel, kernel modules, libraries,