perf evsel: Handle precise_ip fallback in evsel__open_cpu()

This is another patch in the effort to separate the fallback mechanisms
from the open itself.

In case of precise_ip fallback, the original precise_ip will be stored
in the evsel (it was stored in a local variable) and the open will be
retried. Since the precise_ip fallback will be the first in the chain of
fallbacks, there should be no functional change with this patch.

Signed-off-by: Riccardo Mancini <rickyman7@gmail.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/74208c433d2024a6c4af9c0b140b54ed6b5ea810.1629490974.git.rickyman7@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>