perf evlist: Add missing xyarray.h header

It gets it very indirectly, via evsel.h -> counts.h, and since counts.h
doesn't need xyarray.h at all, add it here before we remove it there.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-hkizv6gojwfklj9ezaiiztll@git.kernel.org


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