simpleperf: move CounterSummaries definition to header file.

This is to test it in later CLs.

Bug: 152911261
Test: run simpleperf_unit_test.
Change-Id: I0cdad299654eb36db4a64363335bfa03e54ee7b1
(cherry picked from commit 5271aa719b7cae4cddc9f67803648f17f9b24018)
2 files changed