E.g.:

 $ ./cpu__get_max_freq
 3200000

It does that, as Kan's patch does, by looking at these files:

  $ cat /sys/devices/system/cpu/online
  0-3
  $ ./sysfs__read_ull
  devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq
  /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq=3200000
  $

I.e. find out the first online CPU, then read its cpufreq info.

But do it in tools/lib/api/, so that other tools/ living code can use
it, not just perf.
Based-on-a-patch-by: NKan Liang <kan.liang@intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-915v4cvxqplaub8qco66b9mv@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Renaming libapikfs.a to libapi.a, because it's not just 'fs' specific
library now.
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Tested-by: NSukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Tested-by: NWill Deacon <will.deacon@arm.com>
Cc: Alexis Berlemont <alexis.berlemont@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-g1mk5oj2ayq4vn653ovfg3gv@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Move the libapikfs library building under tools build framework.
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Tested-by: NSukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Tested-by: NWill Deacon <will.deacon@arm.com>
Cc: Alexis Berlemont <alexis.berlemont@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-xjo8r7nuqy9mvlfrmx9zcfwb@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>