perf tools: Fix link time error with sample_reg_masks on non x86

This patch makes perf compile on non x86 platforms by defining a weak
symbol for sample_reg_masks[] in util/perf_regs.c.

The patch also moves the REG() and REG_END() macros into the
util/per_regs.h header file. The macros are renamed to
SMPL_REG/SMPL_REG_END to avoid clashes with other header files.

Signed-off-by: Stephane Eranian <eranian@google.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1441099814-26783-1-git-send-email-eranian@google.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>