simpleperf_report_lib.py: expose in_kernel as bool

This is a slightly nicer interface for Python.

This is a small change split off from a previous investigation on the
bug, which went nowhere, but perhaps this change is useful in isolation.

BUG=200992595
Test: This is dead code so far

Change-Id: Ic4652e27af1c4c3bcc355212be6c11ca1d0498ed
1 file changed