perf tools: Ignore .config-detected in .gitignore

Commit fcfd6611fbccdbf2593bd949097a5c0e45cd96da ("tools build: Add
detected config support") dynamically creates .config-detected. Add it
to .gitignore.

Signed-off-by: Wang Nan <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Zefan Li <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/.gitignore

···
 *-flex.*
 *.pyc
 *.pyo
+.config-detected