kernel: Remove clearing of swap_ok in do_swap()

Removes an unnecessary clearing of the current CPU's swap_ok field
in do_swap() as that clearing is already done at the end of next_up()
which was just called by z_swap_next_thread() a little earlier.

Signed-off-by: Peter Mitsis <peter.mitsis@intel.com>

kernel/include/kswap.h

@@ -124,7 +124,6 @@ static ALWAYS_INLINE unsigned int do_swap(unsigned int key,
 		z_sched_usage_switch(new_thread);
 
 #ifdef CONFIG_SMP
-		_current_cpu->swap_ok = 0;
 		new_thread->base.cpu = arch_curr_cpu()->id;
 
 		if (!is_spinlock) {