Revert "ARCv2: STAR 9000837815 workaround hardware exclusive transactions livelock"

Extended testing of quad core configuration revealed that this fix was
insufficient. Specifically LTP open posix shm_op/23-1 would cause the
hardware livelock in llock/scond loop in update_cpu_load_active()

So remove this and make way for a proper workaround

This reverts commit a5c8b52a.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>