app/testpmd: use clock time in throughput calculation
app/testpmd: use clock time in throughput calculation

The throughput calculation requires a counter that measures
passing of time. However, the kernel saves and restores the PMU
state when a thread is unscheduled and scheduled. This ensures
that the PMU cycles are not counted towards a thread that is
not scheduled. Hence, when RTE_ARM_EAL_RDTSC_USE_PMU is enabled,
the PMU cycles do not represent the passing of time.
This results in incorrect calculation of throughput numbers.
Use clock_gettime system call to calculate the time passed since
last call.

Bugzilla ID: 450
Fixes: 0e106980301d ("app/testpmd: show throughput in port stats")
Cc: stable@dpdk.org

Signed-off-by: Honnappa Nagarahalli <01ccf438b971cc1d8919c8a7f18443cae9429d8b@arm.com>
Reviewed-by: Phil Yang <5a9b6465c065ff0e1fd5d2cb9eb2185e82f34247@arm.com>
Reviewed-by: Ruifeng Wang <a548d51fbc42485a8ba807711a537e88c2b59dd2@arm.com>
Reviewed-by: Ferruh Yigit <ba8734c3c506d2e3557bd4ac8fdaccd25bdb9aa7@intel.com>
Tested-by: Phil Yang <5a9b6465c065ff0e1fd5d2cb9eb2185e82f34247@arm.com>
Tested-by: Ali Alnubani <cf6d2c19745ffe2f5051227a159da6be2e1adaa2@mellanox.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk