eal/linux: use C11 atomics for interrupt status

eal/linux: use C11 atomics for interrupt status

The event status is defined as a volatile variable and shared between
threads. Use C11 atomic built-ins with explicit ordering instead of
rte_atomic ops which enforce unnecessary barriers on aarch64.

The event status has been cleaned up by the compare-and-swap operation
when we free the event data, so there is no need to set it to invalid
after that.

Signed-off-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Harman Kalra <hkalra@marvell.com>