Merge branch 'selftests-expand-txtimestamp-with-new-features'

Jian Yang says:

====================
selftests: expand txtimestamp with new features

Current txtimestamp selftest issues requests with no delay, or fixed 50
usec delay. Nsec granularity is useful to measure fine-grained latency.
A configurable delay is useful to simulate the case with cold
cachelines.

This patchset adds new flags and features to the txtimestamp selftest,
including:
- Printing in nsec (-N)
- Polling interval (-b, -S)
- Using epoll (-E, -e)
- Printing statistics
- Running individual tests in txtimestamp.sh
====================

Signed-off-by: David S. Miller <davem@davemloft.net>