perf tools: Remove brace expansion from clean target

The clean target uses brace expansion to remove some generated files. However,
the default shells on many systems do not support this feature resulting in
some generated files not being removed by clean.

Signed-off-by: Palmer Cox <p@lmercox.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1343598883-17907-1-git-send-email-p@lmercox.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>