perf machine: Use perf_env e_machine rather than arch

perf machine: Use perf_env e_machine rather than arch

The arch string is derived from uname and may be normalized causing
potential differences meaning the ELF machine can be more
precise. Reduce the scope of machine__is as often it is better to use
a thread for the e_machine rather than the machine. Switch from string
to ELF machine constant comparisons.

Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Honglei Wang <jameshongleiwang@126.com>
Cc: Jan Polensky <japo@linux.ibm.com>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>