eal/armv8: fix timer frequency calibration with PMU

eal/armv8: fix timer frequency calibration with PMU

get_tsc_freq uses 'nanosleep' system call to calculate the CPU
frequency. However, 'nanosleep' results in the process getting
un-scheduled. The kernel saves and restores the PMU state. This
ensures that the PMU cycles are not counted towards a sleeping
process. When RTE_ARM_EAL_RDTSC_USE_PMU is defined, this results
in incorrect CPU frequency calculation. This logic is replaced
with generic counter based loop.

Bugzilla ID: 450
Fixes: f91bcbb2d9a6 ("eal/armv8: use high-resolution cycle counter")
Cc: stable@dpdk.org
Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
Reviewed-by: Phil Yang <phil.yang@arm.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>