perf tools: Ignore auto-generated bison/flex files

The commit 65f3e56 ("perf tools: Remove auto-generated bison/flex
files") removed those files from git, so they'll be listed on untracked
files after building perf. Fix it.

Signed-off-by: Namhyung Kim <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: Namhyung Kim

tools/perf/.gitignore

@@ -19,3 +19,5 @@ TAGS
 cscope*
 config.mak
 config.mak.autogen
+*-bison.*
+*-flex.*