perf callchain: Separate perf_reg_value function in perf_regs object

perf callchain: Separate perf_reg_value function in perf_regs object

Making perf_reg_value function global (formely reg_value), because it's
going to be used globaly across all code providing the dwarf post unwind
feature.

Changing its prototype to be generic:

  -int reg_value(unw_word_t *valp, struct regs_dump *regs, int id)
  +int perf_reg_value(u64 *valp, struct regs_dump *regs, int id);

Changing the valp type from libunwind specific 'unw_word_t' to u64.

Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Jean Pihet <jean.pihet@linaro.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1389098853-14466-13-git-send-email-jolsa@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>