test/stack: remove thread synchronisation

test/stack: remove thread synchronisation

Remove the part that checks if there is enough room in the stack, it's
always true as long as size of stack >= MAX_BULK*rte_lcore_count().
This check used an atomic cmpset, and read / write to a shared size
variable. These operations result in some form of synchronization
that might get in the way of the actual stack testing.

Signed-off-by: Steven Lariau <steven.lariau@arm.com>
Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
Reviewed-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Acked-by: Gage Eads <gage.eads@intel.com>