selftests/bpf: Relax time_tai test for equal timestamps in tai_forward

We're observing test flakiness on an arm64 platform which might not
have timestamps as precise as x86. The test log looks like:

test_time_tai:PASS:tai_open 0 nsec
test_time_tai:PASS:test_run 0 nsec
test_time_tai:PASS:tai_ts1 0 nsec
test_time_tai:PASS:tai_ts2 0 nsec
test_time_tai:FAIL:tai_forward unexpected tai_forward: actual 1702348135471494160 <= expected 1702348135471494160
test_time_tai:PASS:tai_gettime 0 nsec
test_time_tai:PASS:tai_future_ts1 0 nsec
test_time_tai:PASS:tai_future_ts2 0 nsec
test_time_tai:PASS:tai_range_ts1 0 nsec
test_time_tai:PASS:tai_range_ts2 0 nsec
#199 time_tai:FAIL

This patch changes ASSERT_GT to ASSERT_GE in the tai_forward assertion
so that equal timestamps are permitted.

Fixes: 64e15820b987 ("selftests/bpf: Add BPF-helper test for CLOCK_TAI access")
Signed-off-by: YiFei Zhu <zhuyifei@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20231212182911.3784108-1-zhuyifei@google.com

selftests/bpf: Add BPF-helper test for CLOCK_TAI access

Add BPF-helper test case for CLOCK_TAI access. The added test verifies that:

* Timestamps are generated
* Timestamps are moving forward
* Timestamps are reasonable

Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
Link: https://lore.kernel.org/r/20220809060803.5773-3-kurt@linutronix.de
Signed-off-by: Alexei Starovoitov <ast@kernel.org>