perf build: Fix 'make clean'

Add some missing files to the 'make clean' target.

Reported-and-Acked-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/8b1f5a5bd66a652be071d423e64aaa994254be31.1449965119.git.jpoimboe@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>