ACPICA: Optimize execution of AML While loops

Previously, a control state object was allocated and freed for
each execution of the loop. The optimization is to simply reuse
the control state for each iteration. This speeds up the raw loop
execution time by about 5%.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>