Move kernelVersion and isAtLeastKernelVersion to a local kernelversion.h,
since we cannot use bpf_headers' version of BpfUtils.
Bug: 202086915
Bug: 157552970
Test: builds
Change-Id: I83149b76cc5125991bdb52ce6160c497eb52b48b
This CL is copying the "generic" parts of BpfUtils to
frameworks/libs/net/common. "Generic" meaning the parts that will be
used by both TcUtils in frameworks/libs/net/common and netd.
Bug: 202086915
Bug: 157552970
Test: atest TetheringTests
Change-Id: I9e780fc22e30d046f44953a8cac7687cb6c721c7