perf tools: Move config/Makefile into Makefile.config

There's no reason to keep it in separate directory now when we moved out
the rest of the files.

Signed-off-by: Jiri Olsa <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Makefile.perf

···
 BPF_DIR		= $(srctree)/tools/lib/bpf/
 SUBCMD_DIR	= $(srctree)/tools/lib/subcmd/
 
-# include config/Makefile by default and rule out
+# include Makefile.config by default and rule out
 # non-config cases
 config := 1
 
···
 FEATURE_TESTS := all
 endif
 endif
-include config/Makefile
+include Makefile.config
 endif
 
 ifeq ($(config),0)
···
 ### Cleaning rules
 
 #
-# This is here, not in config/Makefile, because config/Makefile does
+# This is here, not in Makefile.config, because Makefile.config does
 # not get included for the clean target:
 #
 config-clean: